As you warp a wider variety of material, you’re going to encounter stuff for which the methods described so far simply don’t work for. In the process of making my hobotech mixes, I work with all sorts of old acoustic music that not only fluctuates in tempo, it often includes no percussion, so there’s a serious lack of clear transients as well.
There are a few ways of dealing with this sort of stuff. One method is to focus on a bar or two of audio at a time until it forms a musical sounding loop.
Once you’ve tapped in the tempo, turn the Loop switch on, and set the loop brace to one or two bars:
Play back the clip, and what you’ll probably hear is an uneven loop that has a slight skip or a lump in it as it loops back around to the beginning.
The way most people get tripped up at this point is they start adjusting the loop brace. Don’t do this. Remember, the goal here is to end up with a loop that is exactly one or two bars long. If you adjust the loop brace, you may get the loop sounding right, but you’ll end up with an odd-length loop…
…that won’t combine with other clips properly.
The trick is to leave the loop brace alone, and move the audio to fit the loop. In the example above you can see there’s a transient just to the right of where the loop ends. This is the downbeat of the next bar, and it needs to be moved to the left to line up with the end of the loop:
Now you can move the loop brace ahead by two bars (shortcut: click on it and hit up arrow), and repeat this process with bars 3 – 4 and so on.