Modern Technological and Transmission Developments
Over the next two decades the basic programming approach remained unchanged while the technology used moved forward. Transmission systems changed from power lines first to telephone lines, then to FM commercial radio station subcarriers, and finally to satellite.
During the same time, reel-to-reel tape recordings replaced records, eventually reaching a reel size of 19-inches across on four-track half-inch tape, twice the size of a modern 14-inch reel of digital multi-track tape, running at 3-3/4 IPS. A 7-inch reel of home-recording tape normally contains 1200 feet of standard- 1.5 mil thickness tape, 10-1/2 inch studio reels contain 2,500 feet, and digital multitrack reels carry 5,000 feet, but a 19-inch Muzak reel would carry upwards of 10,000 feet on a single reel. At a speed of 3-3/4 IPS, each track could then play almost nine hours without stopping. Multiplied by four monaural tracks and an auto-reversing system and one tape could play continuously for over three days straight without repeating. This was important because at such an odd tape length, no sequence of songs would ever be repeated in any one work shift at any one time of the day for weeks on end.
Subsequently, extremely large versions of the endless-loop tape later introduced to the market as 8-track tape were used to deliver the programs. Originally recorded at the same speed as an 8-track, these large versions of broadcast tape cartridges carried 4 hours of programming at 3-3/4 IPS.
Tape and player quality developments such as chrome tape and noise reduction allowed the cartridges and tape speeds to shrink, first to the size of an 8-track with eight monaural programs on a tape running at 1-7/8 IPS, to the size of a modern laptop hard drive and a speed of 15/16 IPS used by the Library of Congress for Talking Books. As a result, before they were replaced with cassettes, the last of the tape cartridges were capable of carrying the same 8-1/2 hours per tape as the original 19-inch reels could carry per track.
Shortly thereafter, special-format chromium cassettes were available, recorded at 1-13/16, exactly halfway between the common speeds of 15/16 and normal cassette speed of 1-7/8, to prevent use on unlicensed hardware.
One development of Muzak delivery technology came in the form of pulse-code-modulation programs encoded onto 8mm analog video camcorder cassettes. Since there was no video needed on the extra-wide-bandwidth tape, it was possible to encode two hours worth of music on six separate stereophonic tracks, or 12 monaural tracks in the space. Although not widely adapted for stationary systems, the PCM format was widely used on planes, trains and buses throughout the late 80's and early 90's.
These gave way to special-format CD's of the 90's and early 2000's and were the last and best development in physical media program delivery for Muzak before satellite delivery eliminated the need. In addition, it was the first format to deliver true stereophonic sound to a wide audience, as the 8mm format was mostly used for high-quality mono reproduction except for the occasional classical or jazz program in high-end installations.
Released in the late 80's, each disc was recorded at 38kHz with a sampling rate of 12-bit instead of a normal CD with 44.1 kHz and 16 bit to prevent unlicensed use. As most malls and other public buildings already had a primary as well as a backup music system, when stereo audio was adopted, owners simply wired the primary set for the left channel and the backup set for the right channel, which required no further conversions once satellite became available
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