Though/ Although I’d heard of them and had known that there was a lot of hype around them, I’d never listened to any of their songs.

My favorite tracks/ songs of theirs are (They Long to be) Close to You, Yesterday Once More and Superstar.

Their music is magical and soothing.

Nothing wrong with thr first one, but their gives it a human attachment. Not just the music, but Carpenters (their) music.

It makes me mildly sad and feel nostalgic for a time I never lived in.

I wish I traveled back to the 1970s and went to thea concert. of hers.

My favorites are (They Long to be) Close to You, Yesterday Once More, and Superstar.

The Oxford comma is optional but I personally prefer to always use it. It can change the meaning slightly, for example, maybe people unfamiliar with the carpenters will think the song is called “yesterday once more and superstar”(though I think people can probably tell that’s not the case by common sense haha)

I wish I could traveled back to the 1970s and wentgo to their concert.

Though I’d heard of them and (had) known that there was a lot of hype around them, I’d never listened to any of their songs.

It makes me mildly sad and feel nostalgic for a time I've never lived in.

I wish I could traveled back to the 1970s and wentgo to their concert.

It's impossible to travel back to the 1970's, so it's better to use a conditional construction, i.e. "I wish I could...", "I wish I could/would have...". The construction you used implies that it was possible for you to travel back to the 1970's, which you didn't in fact do.