Hello kind anon ! ✨

That’s a very good question ! 😲 Hmm to be honest, I’m just going with my headcanons here but :

Atom’s favorite song would probably be something like kawa no nagare no youni by Hibari Misora ( https://youtu.be/IP3A_eXlL1E?si=rMuGbG9IQZGoB5CK ) since I hc he loves enka 😄
He would really love old songs from some anime, the ending song of Ganba no Bouken for example ( https://youtu.be/JuLMfxQ6OGo?si=U9SV6kiGaOTc_TEX )
But he can enjoy pop music too ! I just think he would have a sweet spot for songs with a little bit of melancholy in it ☺️

For Tenma, he would love classical music and jazz I think.
I don’t know enough about classical music to be sure what song he would prefer but maybe something like The Toccata and Fugue in D minor by Bach ( https://youtu.be/ho9rZjlsyYY?si=rC9TwUbEzLPufInn ) since he plays the organ 😄
And for jazz, I also don’t know much about it lol but maybe something like “born under a bad sign” by the Big Mama Thornton ( https://youtu.be/Rq0B1gp4ic8?si=ZS4G4auqDhzAzk4M ) but that’s actually blues i think so… he would like jazz and blues then 😄 He would enjoy melancholic songs like Atom but they need more of hmm “force” to it for him to like I think 😅

Atom would prefer songs with a soft sense of sadness while Tenma would prefer songs about expressing strong feelings of despair 🤭

Thank you so much for the question kind anon, take care ! ❤️💕✨