Q: What the heck is a four-track, anyway?
A: A four-track, or (more properly, since some have more than 4) multitrack recorder is an audio tape recorder with the capability of recording each track separately (at the same or different times) and playing them back together, so that complex audio productions can be made.
For instance, let's say you're a lone musician in Rescue, California and work crazy hours so that nobody is around when you want to make music. You start tapping out a beat and record it on track 1. Then you rewind it, and (while listening to track 1 on headphones) record a bass track on track 2. Rewind again, and this time lay down your guitar part on track 3 while listening to the rhythm section play back on tracks 1 and 2. Finally, destroy Western civilization as we know it by attempting to record a vocal on track 4 while listening to everything else.
But now you have 4 tracks, and everyone else listens in stereo. No problem. While playing back the four tracks, you connect the two output jacks of your 4-track to the corresponding input jacks of an ordinary stereo cassette recorder. While listening to the sound going out to the cassette, you adjust the levels of each of the 4 tracks you recorded, as well as the equalization (how much bass or treble is boosted or cut, and at what frequencies) and panning (controlling where each track "sounds like" it is in the stereo soundfield). This is called "mixing down" to two tracks. You record the final result on the cassette, duplicate it, and give copies to your friends, who pretend that it sounds just as good as anything George Martin ever came up with.
The above is essentially what's done for every song, whether you're doing it at home or Eric Clapton is doing it in a fancy huge studio. There are more tracks to be added, and more expensive equipment, and we haven't even talked about effects yet, but basically, that's all there is to it.
Q: OK, what equipment will I need to do all this?
A: You can get started for less than $300 new, and the sky's the limit.
Q: Are the four tracks on the cassette-type recorders each a stereo track or do they each represent a left/right channel? i.e. Is a four-track essentially just a two-track in stereo? Whatever the answer, is it universal throughout all makes and models? And do most four-tracks allow you to apply the sliders to the signal on the way out i.e. will the sliders control the level of the pre-recorded material on playback?
A: First, a four-track cassette multitrack is special because a regular stereo cassette recorder also has four tracks: left and right in each direction. The 4-track cassette simply takes advantage of this by going only in one direction and letting you record on all four tracks individually (or, usually, all at once).
This is universal, although different models may use different speeds and have different track sizes or layouts, so you're not always guaranteed to be able to take a 4-track master from one machine and use it on another. And that doesn't even allow for head alignment differences.
If you use any number of tracks other than four on a cassette, you're using smaller amounts of tape than the format was originally designed for (although the original design was for two tracks; mono in each direction).
All tracks on a multitrack (whether you have 4 or 64 of them) are mono by themselves. When you mix down to stereo (what you call "on the way out"), you have to do the following for each track:
Master the three above simple steps and you, too, can see your name on
top albums! :-)
A few more good pages to read