Not sure if anyone else had experienced this but on my iPhone XS there is serious (as in makes it unusable) distortion when I try and play more than two tracks in Noise. I know the phone is OK as I can play music and films without distortion and I know the tracks are OK because on my iPad I can play the four tracks without any issue. However on my XS, running any more than two tracks results in the distortion. It also makes no difference what music mix I select. If I run three or four tracks at once I get the same result.