Audio Syncing An Old Cassette Tape

[DallasSteve]

This question may amuse some old timers like me.  About 35 years ago I had a microphone, a guitar, a Sequential Circuits keyboard, an old version of Cakewalk I bought on discs in a big box, and a Fostex 4-Track tape recorder.  For those who aren't familiar with that clever piece of technology, as shown in the photo below, you could put a cassette tape into the machine and you could record the 4 tracks all in the same direction.  Normally a cassette tape recorded and played in 2 tracks, but you could flip  it and use the 2 tracks on the other side going in the other direction.

So I recorded my demos back in the 80s and 90s this way.  I am modernizing some of the demos in my new Cakewalk by Bandlab using some old Cakewalk files I've kept for 30+ years.  I want to have my old demos to compare as I work.  But I can't find a few in their 2 track form when I mixed them down.  However, I still have them in their 4 track form.  When I copied my tapes into my computer the machine was only a 2 track machine so I have 2 files for each demo, one forward, one reverse.

I opened them in Cakewalk and it did a great job of flipping the reverse track.  But when I line up the 2 tracks as shown below (they are tracks 3 and 4) then ends of the song are off by about 1 second.  This is because the old tape player mechanism is not perfect and the tape runs at a slightly different speed depending on how much of the tape was wound on the spool.

So I know there is a way to stretch the shorter track a little and line it up.  I think it's probably a little tricky to do that.  Can anyone suggest any tips for getting the tapes aligned as closely as possible?  This doesn't have to be perfect because they are only for me to compare to the new demos, but I plan to keep them and maybe even make a collection of my original demos, so I'd like to do as good as I can with limited time and expense.

Edited May 29, 2022 by DallasSteve

[Lord Tim]

If it's a constant rate, as you said you could stretch the short tracks out to the correct length, but I'd suspect it wouldn't be - tape (especially old tape) will likely be speeding up and slowing down over the duration of the song. That also means the pitch will be doing the same too.

If you really wanted the challenge and didn't mind the pitch issues, you could use AudioSnap and manually drop a transient marker at the start of each bar on each set of 2 tracks and then stretch them out progressively to match.

My advice is to look for a cheap second hand 4-track machine and use that. You'd save more money's worth in time for what it'd cost for the 4-track and get FAR superior results.

[DallasSteve]

13 hours ago, Lord Tim said:

If it's a constant rate, as you said you could stretch the short tracks out to the correct length, but I'd suspect it wouldn't be - tape (especially old tape) will likely be speeding up and slowing down over the duration of the song. That also means the pitch will be doing the same too.

If you really wanted the challenge and didn't mind the pitch issues, you could use AudioSnap and manually drop a transient marker at the start of each bar on each set of 2 tracks and then stretch them out progressively to match.

My advice is to look for a cheap second hand 4-track machine and use that. You'd save more money's worth in time for what it'd cost for the 4-track and get FAR superior results.

Good points.  The 4-track machine would solve the mismatch of tape speed.  I gave this a try yesterday and it worked good enough for what I'm doing.  I set Audio Snap for the track and then I dragged the end of the shorter track to match the longer track.  That came out pretty close but there was some variation of the tracks in the middle.  I didn't try to adjust transient markers at each bar.  I'm not sure what Audio Snap does in terms of stretching, but it seemed to work.  I think the other variations were due to the natural tape differences.  It's probably not worth me buying an old machine for this project.

[Lord Tim]

It's more so the more-granular approach to stretching it out - if you're only adjusting the time of small sections rather the song as a whole, that lets you get in and fix the timing fluctuations a little better as they happen. But yeah, it's never really going to be as good as dumping all of the tracks into CbB at once.