I usually go with Song of Storms from Zelda, but Ive come across three other people who have it so now I need a new one and have no idea what to pick. :/
I usually pick whatever I'm interested in at the moment. I picked a Pokemon town tune before when I first started my town. Then I did a town tune with kpop songs. Then I created one with the clannad theme song. Stuff like that. But I mean if you like song of storms you don't have to change it. There's no need to change it just because of others as stargate said.
I chose "Funky Town" for Pripyat. My town, although bright and pretty with tons of flowers, is named after the real Pripyat, where the Chernobyl nuclear disaster happened. Since Pripyat is still a ghost town almost 30 years later, "Funky Town" seemed to fit.
For my town I chose "Land of Beyond" as my town tune because I named my town Beyond after that song. I also thought it was a good kind of song for a mountain-themed town, which is what I am going for. Also for sentimental reasons.
I chose part of "Classic Sinfonia" for my town tune. It's an orchestra piece that my 7th grade orchestra class did, and I really liked playing that piece.
In Balamb, I have the Hamtaro theme song because it's a town of mostly hamsters, but VanessaMay18 made me the Cleyra song from FFIX, so I'll probably switch to that at some point. And my other town is the music from Daguerreo in FFIX, because it's my favorite town in that game.
I had the Pan's Labyrinth lullaby, the Over the Garden Wall theme, and now I have Little Soldier Boy from Avatar. ^^ And I just changed it to the Gravity Falls theme, hehe.
I made some random town tune up for Lumatown. I remember having it as the Song of Storms at one point, but I can't remember whether or not I had it as the Super Mario Bros. theme once (I know I had it in at least one of my WW and CF towns, but I can't remember if I had it in my NL town).
As for Tomalune, which is my WW town that I haven't played in forever... I can't remember. I think it was just a default one because that town was kinda new the last time I played.
Despite not liking the series very much, I decided to use the theme from the original Halloween movie from 1978. I needed something somewhat creepy for my horror-themed town and found someone had made it, so I just copied that. I've tried making my own tunes before, but they never really come out the way I imagine them.
My theme is Concerning Hobbits from Lord of the Rings. I googled a big list of tunes, and tried some of the ones I recognised on the list before picking my favourite.
I just pick whatever song I like. My town is named Bangtan after a Korean Pop group I absolutely adore so I usually pick a song by them.
But right now I have that one song by DJ Snake....What you want I think it's called.