I'm probably very ignorant in this area Michael but 10 seconds over 3-4 minutes doesn't seem very much
. It breaks down as an1/8th or a 24th ie 4-5% spread out! I'm certain that a lot of players back then would have run a little slow or fast without notice. Does the customer have perfect pitch? the new advantage of digital monitoring? or some other problem? Did it sound "wonky" to you? I suspect not!
Dave W