Spent some time playing with this and really liked the basic idea - really easy to scrub the audio back and forwards as required.
Quality of the sound in the free version suffers when the speed is adjusted but there is an in-app purchase for higher quality, so I decided to part with $$s.
The sound quality is now much improved, but it also seems significantly louder, and I can't see a way to adjust the volume. Running my guitar through AmpliTube I couldn't get a clean sound that I could hear clearly over the Riff Maestro track. Am I missing something?