Ben Nguyen wrote:

I have a bad audio tape that contains both sides of the tape recording
on one side. So when played you can hear both sides at the same time
with one track backwards.

Probably not a bad tape at all. Instead, you're playing the tape with the
wrong tape player.

For example, if you play a 4 track 1/4" wide tape with a two-track 1/4" tape
player, you'll get exactly the results you've described. Try using a true
4-track player.

The tracks on a 4-track 1/4" tape are interleaved. Track 1 & 3 as you go
down the tape are recorded one way. Tracks 2 & 3 are recorded the other way.
If you play this tape with a 2-track player, tracks 1 & 2 will be combined
by the wider tape head in the 2-track player. That will give you exactly the
symptoms you describe.