How can I match tempo & sync of old audio files to Garageband?

HI all,

Final question and it's a doozy. While I know the "general concepts" for trying to accomplish the following, acutally trying to get it to work is frustrating. At first thought that the new Garageband tempo/playing thing would work but I'm not being successful. Perhaps there are better programs for this. I am moderately aware of the beat/slicing/tempo tap programs -- I just don't have the lets-do-it-detail to make it work. Here is the goal.

#0 - New DAW file is created in either Garageband or Logic Pro.

#1 - I have old stereo MP3 and AIFF files digitally dubbed from old cassettes, some recorded 30 and 20 years ago. Most were recorded to click track or drum machine. Newer tracks are MIDI but my first tracks are purely audio.

#2 - I drag an audio file (MP3 or AIFF) into either Garageband or Logic Pro. The track becomes an audio track.

#3 -- I need to edit off the beginnings of these tracks. If Garagebands new tempo sync thing is enabled, you can't seem to do this. Once the track is playing -- the tempo should be moderately consistently (The originals often used a Roland TR 707 ??? drum machine). However, the tempo might not be perfect and I might need flexibility.

So, how do I ACTUALLY DO THIS?

#4 - The goal is to get the NEW song template to match it's tempo to the audio track. The song now has the correct tempo that (hopefully) perfectly matches the original track.

#5 - If this works, the old audio track is like an old temp track that is frozen in place.

#6 - I record new fresh tracks against this backing tracking. Voila, I have a newly semi-produced or at least recorded song based on the old recording.

Sounds easy but the devil is in the tricky details. Thanks for any tips, suggestions, references to forums, blogs, YouTube videos or books.

I am open to other software as well.

Thanks in advance. I'll stop bothering you after this. :-)

John