Mushrooms have always given me some pretty significant audio hallucinations when I've taken them and had a strong trip. The first time I ever used them I went out back to sit on the proch and calm myself down as they were starting to kick in very hard, and though it was quite when I walked out there suddenly I felt like I was spinning more and more in my chair as these sounds of people talking and then screaming and dogs barking and sirens going off and cars crashing just got louder and louder until it was so disorienting that I jumped back up and ran inside. That was on two grams.... Another time on five grams for most of the trip I felt like there was a train constantly roaring by right outside my dorm room window.
Pretty much every time I've ever taken 2C-I it's given me a pretty consistent effect which is applied to both my visual and auditory input: first one side of my perception starts out with everything made very big, loud, or just generally enhanced, while the other side starts out with everything small, muffled, or just dimmed, and then each one slowly begins to slide toward their opposite state, picking up speed as they go until it suddenly snaps at the very end, and then this process begins again in the other direction, ad infinitum. At higher doses it actually makes listening to music sort of frustrating, which is a shame, but the trip itself is still marvelous.
On LSD music is generally just intensified to breathtaking levels, but only at the very highest dose I've taken so far it actually got pretty disharmonious. Different parts of the song would speed up or slow down independently, and some sounds would be raised in pitch while others were lowered, and not proportionally, and there were many sounds that didn't actually exist in the songs along with an absence of sounds that were supposed to be there. It was a little odd to work with at first, but it only lasted for really the first phase of the experience, and as it shifted into the more lucid part music started sounding fantastic again.
With psychedelics in general I also tend to get that effect where the end of at least just one clip of some song you listened to at some point just repeats over and over and over again when you're in silence. It is both interesting and potentially maddening (but not in an overboard way). Usually I use it to keep myself moving to a beat even while walking through nature or something.
Probably the strangest audio hallucination I ever had was on I believe about 750 mg of diphenhydramine (stupid decision), I was at a friend's apartment and he was watching anime, a series that I was actually quite familiar with and had introduced him to. But I wasn't actually watching the screen myself most of the time, and he was watching it in Japanese. I swear, I was hearing all the characters talk in perfect English, but everything they said was complete gibberish. I couldn't help but burst into laughter and ask him what the hell he was watching every time, because I of course forgot. Really strange stuff.
Oh, and on salvia I once had my parents screaming at me constantly while running into my spinning room. Strangely I took this quite calmly, but it was very bizarre.
I also recently experienced the sound effects of nitrous, while on LSD and 4-HO-DiPT. The most prominent features were drastically lowered pitch and lots of echoing, like several times over. I definitely want to go deeper into those....
