From the condition, it's obvious that for levels to have the same music they must be a multiple of 17 levels apart. So, one example is
6 Tricky (Lemmingology) and 10 Taxing (Izzy Wizzy Lemmings Get Busy), which are 34 levels apart.
Not counting the WAFD levels,
I'm not sure you even needed this qualifier.
He didn't.
Which brings me on to my question:
Describe how to pass the "Fun" WAFD using at most 10 diggers. (If you know how to do it in fewer, even better, but "Play the version where they can survive the fall anyway" does
not count -- I want a solution that works on
any version.)