audio stutter with music apps

hi,

i frequently run in to audio stutter to the point that my ipad mini retina iOS 813 only produces distorted sound.

i use various music apps. my test setup was DM1 drum machine tempo synced by little midi sequencer, little midi plays arturia imini and sunrizer synthesizers, arturia isem plays a synced arpeggio. to here, everything usually works fine - despite being five music apps already. but when i start playing a melody on moog animoog synthesizer on top of all this, heavy stuttering occurs. obviously this is too much.

but too much of what? system activity monitor app reads CPU activity with single peaks of 70-90%, most of the time a load of just 40%, RAM is 130MB inactive, 238MB free. so there should be enough resources to get clean audio, i think...

what can i tweak to improve audio performance?

flight mode helps a bit, but not much.

thank you!