fwiw, back in the cassette trading days I fiddled w/ azimuth adjustment by ear. Pretty easy to do imo when the whole tape is off (when the playback deck is not the same as the recording deck). It made a HUGE difference at times, most especially when the tape was encoded w/ Dolby. I guess it's optimal if you have a reference tape or something to get it back to where it should be.
Used to do this on a workhorse Onkyo deck and a NAK don't remember the model.
/Ken