midi to audio align

Hello,
I am new to Sonar, so be patient.
now I am starting to make midifiles from songs.
the reason is that not all songs can be found on midifiles and some midifiles are really bad.
I import the audio song into Sonar as a reference.
then I set the project tempo. but here the trouble starts, since audio songs have no steady tempo flow.
I can set an average tempo but that is it.
now my question is how do I align the audio to midi project tempo or have the midi tempo change to the audio tempo changes?
this is a complete song not audio parts.
what is the best to do? have mutiple midi tempos or change the audio tempo?
I have seen a video on samplitude that a guy set up multiple midi tempo changes (with markers) to the audio to get all in sync.
is there a good tutorial how to do it? where can i find it?
what is the best way to go about this?
greetings to all
 
Loekie

I hate to admit this but I've never yet used AudioSnap. The way I do the job is to use a (hardware) metronome to find the approximate tempo. I then play a simple MIDI drum beat track along with the audio, sync them up at the beginning and vary the tempo until I get a good match.

If the audio original used a click track, this works fine as there's a single fixed tempo and it's usually a whole number of beats per minute. However, many older recordings have variable tempo. In this case I insert new tempos at appropriate points until I get a good match. This is time consuming but ultimately it works. Luckily I don't charge by the hour: I do this as a hobby!

For the purposes described (fitting MIDI tracks to a song) you don't have to be spot on, as the finished product will be the MIDI on its own.