How can I learn to hear the inner voices more clearly in dense harmonies (like sax soli or whatever) without confusing myself? I mean, how to mentally separate the lines
it probably won't sound like separate coherent lines, but if you want to get stronger at hearing harmonies, just transcribe it. use brute force, unpause-pause, hunt and peck method. you will gradually get stronger and start to learn many interesting things about life as you go