I remember seeing a different post somewhere online asking about the same issue a while ago but can no longer seem to find it so decided to ask myself. I’ve experienced this many times with multiple songs and I’ve never heard it within any songs from other artists that I listen to. Basically, whenever there is a quiet part in a song that I am working on, say a sub bass and a quiet, subtle synth in the background, as soon as a louder synth or drums ( eg. hi-hat ) starts playing, there is a sudden spike in volume with the quiet elements. It is only noticeable when playing on my phone, or at least not as noticeable through headphones/ tablet speakers, even on standalone speakers. I thought it could have something to do with compression applied to the specified quiet synth, but switching that off didn’t solve my problem. Has anyone else experienced this and how can I get rid of this behavior?