This material has been adapted from "101 Terms: A Glossary of Tape Recording Terms," published by the Magnetic Products Division of the 3M Company. Our .thanks for their permission to bring it to you.
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1. Acetate Base - The transparent cellulose-acetate plastic film that forms the backing for many magnetic recording tapes.
2. Automatic Reverse - The ability of some four-track stereo tape recorders to play the second pair of stereo tracks automatically (in the reverse direction) without the necessity for interchanging the empty and full reels after the first pair of stereo tracks is played. (See also Four-Track Recording)
3. Automatic Shut-Off - A device (usually a mechanical switch) incorporated into most tape recorders that automatically stops the machine when the tape runs out or breaks.
4. Azimuth Adjustment - The mechanical adjustment of a magnetic head whereby exact alignment of the head gap with a standard tape-recorder magnetic pattern is achieved. Of prime importance for optimum high-frequency performance and recorder-to-recorder playback compatibility. (See also Head Alignment)
5. Azimuth Loss - The signal loss caused by lack of alignment between the playback-head gap and the signal recorded on the tape.
6. Backing or Base - The flexible material, usually cellulose acetate or polyester, on which is deposited the magnetic-oxide coat that "records" the taped signal.
7. Bias - A constant signal or tone added to the audio signal during recording to circumvent the inherent non-linearity of magnetic systems. The best (and most commonly used) bias is a high-frequency (usually 50,000 to 100,000 Hz) alternating current fed to the recording head along with the audio signal to be recorded.
8. Bulk Eraser or Degausser-A hand-held (or larger) device used to erase magnetic tape without removing it from the reel. It generally produces a strong alternating magnetic field that neutralizes all previously recorded magnetic patterns on the tape.
9. Cartridge - A sealed plastic container that holds tape of V-i-inch or narrower width. Designed to eliminate manual tape threading, cartridges operate on either the continuous-loop (single hub) principle or the reel-to-reel (double hub) system. Cartridge machines are usually smaller and simpler to use than ordinary open-reel units. (See also Cassette)
10. Capstan - The driven spindle or shaft in a tape recorder - sometimes the motor shaft itself-which rotates against the tape (which is backed up by a rubber pressure or pinch roller), pulling it through the machine at constant speed during recording and playback modes of operation. The rotational speed and circumference of the capstan determine tape speed.
11. Cassette - A type of tape cartridge operating on the hub-to-hub principle and now coming into wide use in portable and home machines.
12. Crosstalk - The undesired pickup of a signal from an adjacent track recorded on a tape.
13. Deck, Tape -  A tape recorder designed specifically for use in a high-fidelity music system. It usually consists only of the tape-transport mechanism and preamplifiers for recording and playback. It does not include power amplifiers or speakers.
14. Decibel  - Abbreviated "dB" or "db," it is a relative measure of sound intensity or "volume." It expresses the ratio of one sound intensity to another. One dB is about the smallest change in sound volume that the human ear can detect. (Also used to express volt^ age and power ratios.logarithmically.)
15. Dolby - An electronic device or circuit that reduces the amount of noise (principally tape hiss) introduced during.the recording process. It does this by boosting - in carefully controlled amounts  - the strength of weak signals before they are recorded. During playback the signals (and the noise) are cut back by an exactly equivalent amount. The original dynamics are thus restored, but the noise is reduced by 10 to 15 dB. At one time found only in recording studios, simplified Dolby circuits designed especially for tape recording are now available to the audiophile as accessories or built into tape machines.
16. Dropout - During playback, the momentary loss of a recorded signal resulting from imperfections in the tape. These may take the form of non-magnetic foreign particles imbedded in and flush with the tape's surface. However, these imperfections are most commonly high spots on the tape surface that push the tape away from the magnetic head, thereby increasing the area affected (the "umbrella" effect).
17. Dual-Track Recorder - Usually a monophonic recorder with a recording-head gap that covers somewhat less than half the width of a standard quarter-inch tape, making it possible to record one track on the tape in one direction and (by turning the reels over) a second track in the opposite direction. Also known as "two-track" or "halftrack."
18. Dub - A copy of another recording.
19. Dynamic Microphone - An electromagnetic pressure microphone that employs a moving coil in a magnetic field to convert sound pressure to electrical energy in a manner similar to that of an electric generator. Impedance and output are generally lower than those of the ceramic or crystal microphone types. Low impedance permits the use of longer connecting cables without high-frequency loss or hum pickup.
20. Dynamic Range - The voltage ratio (expressed in decibels) between the softest and loudest sounds a tape recorder or other device can reproduce without undesirable distortion in loud passages and excessive noise in soft ones-.
21. Echo  - A special facility .found in some three-head tape recorders. Part of the slightly delayed output of the monitor head is fed to the recording head and mixed with the signal being recorded. The result is an "echo" of the material recorded a moment before.
22. Editing  - The alteration of a tape recording by physical means to eliminate or replace undesirable portions, add portions not present in the original, or otherwise rearrange the original. Magnetic tape is unsurpassed for editing purposes, since it can be easily cut and spliced.
23. Equalization - The selective amplification or attenuation of certain frequencies. Also refers to recognized industry standards for recording and reproducing "characteristics" (such as the NAB Standard), the proper use of which can assure uniform reproduction of prerecorded tapes and improvement of a system's signal-to-noise ratio.
24. Erasure - The neutralization of the magnetic pattern on tape by use of a strong magnetic field, thereby removing the recorded sound from the tape. During recording, the erase head on a recorder automatically removes any sound previously recorded on the tape just before the tape reaches the record head. (See also Bulk Eraser)
25. Extra Play-Also called "long play" or "extended play." Refers to tape that gives more than standard playing time on a standard reel because it employs a thinner base together with a thinner bul usually more responsive oxide coating, and thus more tape can fit onia reel.
26. 'Fast Forward-The provision on a tape recorder permitting tape to be run rapidly through it in the normal play direction, usually for I search or selection purposes.
27. Feed Reel-Also called "stock," "supply," or "storage" reel. The reel on a tape recorder from which the tape is taken as the Machine records or plays.
28. Flutter - Very short, rapid variations in tape speed, causing pitch and volume variations that were not present in the original sound. A form of distortion.
29. Four-Channel Sound-Stereo produced by four loudspeakers, each being fed a different signal. At present four-channel tape machines are equipped with special heads and electronics that enable them to play back - and sometimes record - four tracks at a time.
30. Four-Track or Quarter-Track Recording-The arrangement by which four different channels of sound may be recorded on quarter-inch-wide audio tape. These may be recorded as four separate and distinct tracks (monophonic) or two related (stereo) pairs of tracks. By convention, tracks 1 and 3 are recorded in the "forward" direction of a given reel, and tracks 2 and 4 are recorded in the "reverse" direction. (See also Four-Channel Sound.)
31. Frequency-The repetition rate of cyclic energy, such as sound or alternating electrical current, expressed in cycles per second (hertz or Hz) or thousands of cycles per second (kilohertz or kHz). By c'on-. vention, "bass" frequencies in music extend from about 20 to about 200 Hz. "Treble" sounds are at the high-frequency extreme of the sound spectrum and may extend from 2 or 3 kHz to the frequency limit of audibility (about 18 to 20 kHz). "Middle" (or mid-erange) frequencies occupy the remainder of the spectrum, from 200 Hz. to about 3 kHz.
32. Frequency  Range-The  span between the highest and lowest ,  pitched sounds that a tape recorder or other sound-system component can reproduce at a usable output or volume level.
33. Frequency Response  - Always specified as a range, such as 50 to 15,000 Hz; but in order to be meaningful it must be further defined in terms of decibel variation from absolute flatness over a specified frequency range (e.g., ±3 dB from 50 to 15,000 Hz). An indication of a sound system's ability to reproduce all audible frequencies supplied to it, maintaining the original balance among the low, middle (or mid-range), and high frequencies.
34. Full-Track Recording-Applies to quarter-inch-wide (or less) tape only. It defines track width as essentially equal to tape width.
35. Gain-The voltage ratio of the output level to the input level for a system or component of a system. Usually expressed in decibels.
36. Gap-The effective distance between opposite poles of a magnetic head, measured in microinches or microns. Especially critical for playback heads in which gaps must be narrow in order to resolve (reproduce) high-frequency (short wave-length) signals. Recording heads generally have wider gaps than reproducing heads.
37. Harmonic Distortion - Distortion characterized by the appearance in the ouput signal of spurious harmonics of the fundamental frequency. Usually expressed as a percentage of the output signal.
38. Harmonics-Overtones that are integral multiples of the fundamental frequency. In properly balanced a.c.-biased tape recorders, only the odd-order harmonics (primarily the third) are generated by the recording process and these are very low in amplitude.
39. Head-In a magnetic-tape recorder, the generally ring-shaped electromagnet across which the tape is drawn. Depending on its function, it either erases a previous recording, converts an electrical signal to a corresponding magnetic pattern and impresses it on the tape (record function), or picks up a magnetic pattern already on the tape and converts it to an electrical signal (playback function). Most home recorders have a separate erase head, but combine the record and play functions in a single unit. Professional machines and those intended for the serious amateur have separate heads for erase, record, and playback.
40. Head Alignment- Includes all mechanical adjustments necessary to assure proper spatial relationships between the head gaps and the tape-or, more specifically, a properly recorded tape track. It may be separated into five attributes describing correct head attitude. See Fig. 1.
41. Head Demagnetizer or Degausser - A device used to neutralize possible residual or induced magnetism in heads or tape guides. Unless the recorder has an automatic head-demagnetizing circuit and non-magnetic tape guides, periodic use of a. head demagnetizer may be necessary to avoid addition of hiss noise to, or even partial erasure of, prerecorded tapes.
42. Hiss - A high sibilant sound, most often found in tape recording or tape playback. The better the tape system, the lower the hiss.
43. Impedance The resistance to the flow of alternating current in an electrical circuit, generally categorized as either "high" or "low," but sometimes given in ohms or millions of ohms (megohms). Commonly used to rate electrical input or output characteristics of component so that proper "match" can be made when interconnecting two or more devices (such as a microphone, tape recorder, and loudspeaker). Power loss or frequency discrimination can result from a "mismatch" of impedances between two units.
44. Index Counter-An odometer type of counter that indicates revolutions (not feet of tape), usually of the supply reel, thereby making it possible to index selections within a reel of tape and readily locate them later on a given machine.
45. Input Signal-An electrical voltage embodying the audio information that is presented to the input of an amplifier, tape recorder, or other electronic component.
46. Input - The terminals, jack, or receptacle provided for the introduction of the electrical input signal voltage into an amplifier or other electronic component.
47. Intermodulation Distortion - Distortion that results when two or more pure tones produce new tones with frequencies representing the sums and differences of the original tones and their harmonics.
48. Ips - Abbreviation for tape speed (inches per second).
49. Jack - Receptacle for a plug connector leading to the input or output
50. circuit of a tape recorder or other piece of equipment. A jack matches a specific plug.
51. kHz - Abbreviation for kilohertz, or one thousand cycles per second. For example, 19 kHz equals 19,000 Hz.
52. Leader and Timing Tape - Special tough non-magnetic tape that can be spliced to either end of a magnetic tape to prevent its damage and possible loss of recorded material. Either white or in colors, it usually has some type of marking that enables it to be used as a timing tape. It therefore can be spliced between musical selections to provide desired pauses in playback.
53. Level Indicator - A device on a tape recorder for indicating the level at which the recording is being made; it serves as a warning against under- or over-recording. It may be a light indicator or a meter. (See also VU Meter)
54. Low-Noise Tape - Magnetic tape with a signal-to-noise ratio 3 to 5 dB better than conventional tapes, making it possible to record sound (especially wide-frequency-range music) at reduced tape speeds without incurring objectionable background noise (hiss) and with little compromise of fidelity. Additional characteristics of most low-noise tapes include extremely good high-frequency sensitivity and a heavy-duty binder system for reduced ruboff of magnetic oxide and an increase in wear life over ordinary tapes.
55. Low-Print Tape - Special magnetic recording tape significantly less susceptible to print-through (the transfer of signal from one layer of tape to another), which results when tape is stored for long periods of time. These tapes are especially useful for "master recording" (making an original recording from which copies will be made) on professional-quality equipment.
56. Mil - One one-thousandth of an inch. Tape thickness is usually measured in mils.
57. Mixer - A device that allows two or more signal sources to be blended, balanced, and fed simultaneously into a tape recorder or amplifier.
58. Monophonic (Monaural) Recorder - Refers to single-channel recorders, as distinguished from stereophonic types. Current home recorders are  almost all  of the four-track stereo configuration.
59. Monitor Head - A separate playback head on some tape recorders that makes it possible to listen to the material on the tape an instant after the recording is made and while the recording is still in progress.
60. NAB Curves  - Standard tape-recorder playback equalization curves established by the National Association of Broadcasters. (See also Equalization)
61. Noise - Unwanted electrical signals produced by electronic equipment, and rough or non-homogeneous oxide coatings on magnetic tape. Mostly confined to the extremes of the audible frequency spectrum where it occurs as hum and/or hiss, it may be reduced by good machine and tape design. (See also Low-Noise Tape)
62. Noise, Weighted-The noise measured within the audio frequency band using a measuring instrument that has a frequency-selective characteristic. The frequency sensitivity of the instrument is adjusted to correspond to that of the average human hearing response.
63. Open Reel - Tape systems that, for home applications, use up to 7-inch reels of tape. To start the tape, it must be threaded by hand from the full to the empty (or takeup) reel. Open-reel tape systems usually provide greater fidelity than cassette or tape cartridge systems, but that gap is closing rapidly. (See Tape Speed)
64. Output (also Maximum Output Level)-The useful signal delivered by a recorder using a particular type of tape, usually at an arbitrarily fixed level of harmonic distortion (1 or 3 per cent; and relative to the performance of a tape with standard characteristics (such as Scotch No. 111).
65. Oxide - The ferro-magnetic particles which, when properly dispersed in a plastic binder and coated on a backing or base, form the magnetic portion of magnetic tape. Conventional oxide particles are chemically known as gamma ferric oxide, are brown in color, acicu-lar (needlelike) in shape, and of micron length. .Less conventional
66. oxides have been developed that exhibit significantly different magnetic properties (and size).
67. Patch Cord  -  Sometimes called "signal lead." A short shielded wire or cable with a plug on either end (or with a pair of clips on one end) for conveniently connecting together two pieces of sound equipment such as a phonograph and tape recorder, an amplifier and speaker, etc. Not to be used for 120-volt current.
68. Pause Control - A feature of some tape recorders that makes it possible to stop the movement of tape temporarily without switching the machine from "play" or "record."
69. Playback - The reproduction of sound previously recorded, on a tape. The opposite of record.
70. Playback Head - Magnetic head used to pick up a signal from a tape. Often the same head as is used for recording, but with its circuits changed by means of a record/play switch which also energizes the erase head. (See also Head)
71. Polyester Base - A plastic-film backing for magnetic tape used for special purposes where strength and resistance to temperature and humidity change are important. (Mylar is a du Pont trade name for their brand of polyester.)
72. Portable Recorder - Originally, any tape recorder designed for easy mobility and requiring connection to a 120-volt a.c. supply for operation. Recently the term has been applied specifically to battery-powered units that do not require external power for operation.
73. Prerecorded Tape - Tape recordings that are commercially available and generally embody the same material that is available on phonograph records.
74. Pressure Pad - A device that forces tape into intimate contact with the head gap, usually by direct pressure at the head assembly. Felt or similar material, occasionally protected with self-lubricating plastic, is used to apply pressure uniformly and with a minimum of drag on the backing (non-coated) side of the tape.
75. Pressure Roller - Also called "pinch roller" or "capstan idler." A hard-rubber roller that holds the magnetic tape tightly against the capstan, permitting the latter to draw the tape off the supply reel and past the heads at a constant speed. (See also Capstan)
76. Print-Through - Undesired transfer of magnetic pattern from layer to layer of tape on a reel. In most cases, will make recording unusable.
77. Raw Tape - A term sometimes used to describe tape that has not been used for recording. Also called "virgin" or "blank."
78. Reel-to-Reel - Designates those tape machines that do not use a cartridge or cassette. (See also Open Reel)
79. Rewind Control - A button or lever for rapidly rewinding tape from the takeup reel to the supply reel.
80. Saturation - The condition reached in magnetic tape recording where output does not increase with increased input, and hence distortion increases significantly. Useful for defining reference output levels, since it is independent of bias current.
81. Sensitivity - As used to describe the capabilities of raw tape, it indicates the relative output for a given input in the linear (low-distortion) portion of a tape's magnetic transfer characteristic. Sensit vity data plotted as a function of frequency (or wave length) gives frequency response, usually relative to a standard reference tape.
82. Separation - The degree to which two stereo signals are kept apart. Stereo realism depends on the successful prevention of their mixture in all parts of a hi-fi or tape system. Tape systems have separation capability superior to that of disc systems.
83. Signal-to-Noise Ratio-The voltage ratio, usually expressed in decibels, between the loudest undistorted tone recorded and reproduced by the recorder and the noise reproduced when the audio signal is reduced to zero.
84. Sound-on-Sound - A method by which material previously recorded on one track of a tape may be re-recorded on another track while simultaneously adding new material to it.
85. Splicing Block-A metal or plastic device incorporating a groove within which ends of the tape to be spliced are held. An additional diagonal groove provides a path for a razor blade to follow in cutting the tape. It makes splices very accurately using narrow-width (Vax") splicing tape. (See also Tape Splicer)
86. Splicing Tape - A special pressure-sensitive, non-magnetic tape used for joining two lengths of magnetic tape. Its "hard" adhesive will not ooze, and consequently will not gum up the heads or cause adjacent layers of tape on the reel to stick together.
87. Squeal - The audible noise caused by alternate sticking and release of tape. It may occur at heads, pressure pads, or guides where friction develops with the face or back side of a magnetic tape. It is largely eliminated by regular cleaning of suspected surfaces and by using a tape employing a built-in dry silicone lubricant.
88. Takeup Reel-The reel on the tape recorder that accumulates the tape as it is recorded or played.
89. Tape Guides - Grooved pins or rollers mounted between and at both sides of the tapehead assembly to position the magnetic tape correctly on the head as it is being recorded or played.
90. Tape Lifters-A system of movable guides that automatically prevents the tape from contacting the recorder's heads during fast forward or rewind modes of operation, thus preventing head wear.
91. Tape Loop - A length of magnetic tape with the ends joined together to form an endless loop. Used either on standard recorders, special "message-repeater" type units, or in four- or eight-track cartridge devices, it makes possible the repetitive playback of a recording without rewinding the tape.
92. Tape Monitoring - See Monitor Head
93. Tape-Transport Mechanism - The platform or deck of a tape recorder on which the motor (or motors), reels, heads, and controls are mounted. It includes those parts of the recorder other than the amplifier, preamplifier, loudspeaker, and case.
94. Tape Player-A unit that is not capable of recording and is used only for playing prerecorded tapes.
95. Tape Speed - The speed at which tape moves past the head in recording or playback modes. Standard tape speed for home use is W2 ips or half that speed (33A» ips). Speeds of IVu and 15/i6 ips are found on some machines, but on reel-to-reel recorders are usually suitable only for non-critical voice recording. Some cartridge machines, using special tape and circuits, achieve very good results at the slow speeds. Professional recording speed (for making original master tapes of music, for-example) is usually 15 ips and sometimes higher.
96. Tape Splicer - A device, similar to a film splicer, for splicing magnetic tape automatically or semi-automatically. Different models vary in operation, most using splicing tape; some professional units employ heat. (See also Splicing Block)
97. Telephone Pickup - Any of several devices used to feed telephone conversations into a tape recorder, usually without direct connection to the telephone line and operating by magnetic coupling.
98. Tensilized Polyester-A polyester tape backing that has been pre-stretched principally in the lengthwise direction to increase resistance to further stretching.
99. Tone Controls-Control knobs on a tape-recorder amplifier used to vary bass and treble response to achieve the most desirable balance of tone during playback.
100. Track-The path on the magnetic tape along which a single channel of sound is recorded.
101. Two-Track Recording-On quarter-inch-wide tape, the arrangement by which only two channels of sound may be recorded, either as a stereo pair in one direction or as separate monophonic tracks (usually in opposite directions).
102. Uniformity-In terms of magnetic tape properties, a figure of merit relating to the tape's ability to deliver a steady and consistent output level when being recorded with a constant input. Usually expressed in decibel variation from average afa mid-range frequency.
103. VU Meter-A "volume unit" meter that indicates audio-frequency levels in decibels relative to a fixed O-dB reference level. The meter movement differs from those of ordinary voltmeters in that it has a specified ballistic response adapted to monitoring speech and music. Used in many home and most professional recorders to monitor recording levels and maintain them within the distortion limits of the tape.
104. Wave Length - In tape recording (and referring specifically to the tape magnetization created by pure single-tone recording), the shortest physical distance between two peaks of the same magnetic polarity; also, when expressed in mils, the ratio of tape speed (in ips) to recorded frequency (in kilohertz).
105. Wow  - A form of distortion in sound-reproducing systems caused by relatively slow periodic variation in the speed of the medium (such as tape) and characterized by its effect on pitch.
106. Wrap-The length of the tape's path along which tape and head are in intimate physical contact. Sometimes measured as the angle of arrival and departure of the tape with respect to the head. A "good wrap" means a good tape-to-head-gap relationship. (See also Head Alignment)   

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