Comment Re:I learned of this from Frank Zappa (Score 2) 25
SMPTE timecode was (and sometimes still is) used to synchronize two playback machines. AFAIK the original intention was to help lock film or video editing machines to an external tape recorder, e.g. you'd record the final master for a movie score on 1/4" audio tape with two tracks and digital timecode data in the middle. If the film or video also has SMPTE timecode data you can use this to determine the time difference between them and keep them in sync by adjusting the capstan motor.
If you had two 24-track tape machines in a recording studio, you use the same principle to get 46 tracks by striping timecode data on track 24 on both machines, and again, a synchronizer unit can ensure they run together. War of the Worlds was done this way and was probably one of the first. I think the world record was 5 24-track machines slaved together, which must have made mixing an absolute nightmare.
Later you could get a box that would decode an SMPTE timecode into MIDI timecode. That way, before using a DAW was feasible, you could compose a song on a computer, using it to control a bunch of synthesizers, and overdub them to tape. Using an SMPTE timecode you'll ensure that the computer can chase the tape and the timing will be perfect each time even if the tape speed drifts slightly, which it does.
More recently, modern DAWs can actually decode SMPTE in software, when you're importing a project from tape, or doing a hybrid tape/DAW project.
I use SMPTE for both sequencer timing and to lock two tape machines together. Obviously I could do this with a lot less effort on a single laptop, but I get a kick out of doing things the old way.