faint precession of sound on vinyl

Deaf_j...The playback stylus does not "read the adjacent wall". It is reading its current groove, but that groove was corrupted by the adjacent groove when the record was cut.

As to which channel is affected...it is horizontal groove modulation (mono) which is the problem. (Vertical groove modulation doesn't affect groove spacing). So, the pre-echo signal will be the mono component of the next groove.

Tails out
A term describing a reel of tape wound with the end of the audio toward the outside of the reel. Tape stored in this manner is less likely to have audible print-through, since the tape must be rewound before playback. Any print-through that does happen to occur will sound after the original sound (instead of before), which is less problematic.

Rwwear...I take your point about rewinding the tape, although I don't see how this would erase any print=through.

However, whichever way the tape is wound the first few seconds of music will be next to the second few seconds, and print-through will be the same. The echo, be it groove distortion or mag tape print through, occurs both before and after, but it only becomes audible before the begining of the music because there is no sound to mask it.

I am no expert on Reel to Reel but tails out was used for mix down engineers for years to prevent pre-echo. It doesn't fix tapes that already have pre-echo and doesn't work for 4 track tapes that play in both directions. Pre-echo that may have existed on analog recordings can easily be fixed when mastering to CD in the digital domain by the way. This would explain why most CDs don't have it.