All Star Music's layout is such that it is more spread out than the other two All Stars. I am not sure how much more spread out it is than Pop but to me it seems to be that way. As far as rooms, Pop has 2880 rooms, Music has 1920 so it would reason it would have to be bigger. Yet ASMU seems to have more landscaping than the other values, so that takes up room and makes it more spread out. I have stayed at both and do think Music seems more spread out. I did get a preferred room last week at Music and I loved it. We were in Calypso (room1425) but not right on the pool. I have stayed preferred at Pop, Sports and Music and was only near a pool at Pop and that was above the baby pool and it wasn't noisy. Last week the pools were pretty crowded until midnight and still had people in them past midnight. So you have late night swimmers at that resort for sure. But in my room in preferred, I coudn't hear a thing. I will never not pay for preferred at a value again, since they only have one bus stop and we like to be close to the food court its worth it to us. If you were way out in say the Country Fair section of Music, that would be a hike. We stayed in the Rock Inn section a couple of years ago and that was bad enough!
I think Music is quieter than Pop, I can't say for sure but I would swear those rooms are more soundproof than Pop's. I love Pop but do have to say our room(s) there have let in more noise from the outside and our neighbors than the All Stars.
Maybe someone can give you the exact dimensions of the overall size of ASMU. I know that Pop is spread out on 177 acres, (saw that on allearsnet) but not sure what the acreage of Music is.