Right now, I'm really digging K.K. Disco, both the live version and the version you can buy. The version you can buy songs a lot like the music I already listen to. But all of K.K.'s are so good.
Disco is good. I also like Two Days Ago, Lullaby, Bubblegum, I Love You, Aria, Etude, Lament, Metal, Rock, Rockin, Ragtime, Only Me, and Stroll. But my favorite is Stale Cupcakes. I really love the cover art for almost all of them too. I think they did an awesome job with the music in this game, and the CD's, art, even KK's performance versions--it's all really good and fun in my opinion.