Thanks for your hard work, i've downloaded your K-on songs and there are few songs I would love to get as cdlc as well, one is Seishun Study - this is the OP1 of the We Never Learn anime. Here is the youtube link of the bass cover, its bass line is somewhat fun to hear.
Another one is Sparkle (Movie Version) by RADWIMPS, you can check the music sheet here: https://musescore.com/user/3443166/scores/5910045
Lastly, I noted that you already have the TV size edition of Wagamama Mirror Heart by Ohashi Ayaka, it would be great if there is also a full version for that.