I'm designing an interface for an Android app that would allow the user to control the pitch, tempo, volume, etc. of some music playing in the background.
Here's what I've sketched so far:
I avoided using sliders in an attempt to make the UI less cluttered. However, I still want users to be able to change the values of parameters by sliding horizontally across any of them (in addition to being able to click on a +/- button).
E.g., to increase the Volume, you would place a finger on 34% and slide towards the right.
Is there a way to ensure that the user knows about this 'hidden' affordance? Or has anyone seen something similar implemented on an existing application (iOS or Android)?