I can really relate to this, and I tend to consider listening to the same song over and over a stim because, like you, I also engage in other stims whilst doing it sometimes, and it really calms me down (particularly when I am stressed) and that is the reason why I do it. I think my record for listening to the same song repetitively is something like 8 hours straight or something ridiculous. Again, like many stims, I think some neurotypicals may engage in this behavior as well, but they don't do it for the same reasons autistic people do it, and it probably isn't as repetitive. Gotta love that replay button...... 
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Hi! I'm Stampy (not the actual YouTuber, just a fan!) and I have been diagnosed professionally with ASD and OCD and likely have TS. If you have any questions or just want to talk, please feel free to PM me!
Current Interests: Stampy Cat, AGT, and Medicine