What is "crosstalk"?

Question

In Music Production by Hans Weekhout, he says

"People discovered that manipulating instruments was more effective by separating them acoustically. To minimize crosstalk, acoustic screens (gobos) were positioned between instruments. Multitracking became the standard."

I then found in aforum the following comment:

"When separate signals are recorded on two or more channels of magnetic tape, the signal on one channel may be picked up during playback on another channel. This effect is called crosstalk or leakage."

"Because of the close spacing of channels on tape, recorded signals cannot be completely separated during playback (even with the small space between the positions of the channels on tape), and thus some crosstalk is inevitable."

Source: http://www.tapeheads.net/showthread.php?t=48908

So I thought to myself,

Imagine you wish to record two musicians using multitrack recording. You have Performer A and Performer B with Mic A and Mic B respectively. Now, suppose the performers are standing next to each other and their mics are nearby. Then Mic A will not only pick up Performer A but also Performer B, thus failing to capture their signals separately.

Is this an accurate description of crosstalk? If not, what is crosstalk?

Answer 1

Your assumption is correct - unwanted 'noise' from a nearby signal being heard in the primary mic/track.

In short, noise from one source 'talks' loud enough to be heard by another… cross-talk.

This is, of course, easiest to understand for microphones as you can equate it with what you would hear with your own ears if you moved from one location to the next.

Analogue tape recorders exhibit a similar issue, but magnetically, because the tape tracks are close enough to each other for 'stray' magnetic fields directed to one track being strong enough to influence neighbouring tracks.

Back in the early days, sonic isolation or "mixing" was still an issue, even when only one mic was placed in a recording studio. Think back to Glenn Miller or early Elvis.
The solution back then was to change the number of instrumentalists of one type - Miller's multiple saxophones - move the mic… or move the drum kit away from the mic so it's not drowning the singer ;)