No idea, I wish I knew too ):~ Sometimes I have to stand in there all day and just write down the lyrics to google it & still nothing. If your H&M is really friendly, when the song you want is playing, you can ask the manager to go in the back and see what the song is for you because it normally says on their music player. Aside from that & without the Shazam App on an iPhone, no idea. A lot of the retail stores generally play the same music if you stand in there for a long time. I think Forever 21 sometimes has the same songs as H&M too?

Sometimes they're also like remixes of songs specifically made for the store, so its also harder to find. A lot of it is also hipster music, so for that genre and remixes, try hypem.com or soundcloud.com

Sorry D: