There are a zillion out there. Best way is to try a few and see [u]which one is preferred fit for[/u] you.

The usual caveat that none they're all either plagued with adds or "in-app purchases", so a modest purchase is necessary for any you'll likely want to use.

I tried a few and ended up using Music Speed Changer for a while. I still have it installed. It's KIS in keeping with my philosophy, has a straighforward easy to use clean interface without the bling or superflous to purpose gimmicky 'features'.