Currently, when increasing/decreasing the volume in the UI, the volume switch abruptly between the two volume settings, which is not “pleasant”, probably because we are used to the smooth transition of turning a volume knob.
Ideally, changing the volume should be handled by a separate thread who increase the volume at a fixed rate, to simulate turning a volume knob. Something like a 1 second transition from 0 to 100 (or 0.5 second from 20 to 70) would be close to the usual transition of turning a volume knob.
While we are at it, a “mute” button which reduce the volume to a configurable volume setting so when the phone ring or someone knock at the door while we are enjoying our preferred track we could “mute” it to 10 or 20 and keep enjoying our preferred track while we answer the phone or the door.