this is just all the K-ON songs from memory
OPs/EDs and songs on the singles
Cagayake Girls
Happy Sorry
Don't say lazy
Sweet Bitter Beauty Song
Go Go Maniac
Genius!?
Listen
Our Magic
Utauyo Miracle
Kira Kira Days
No, Thank You
Girls in Wonderland
Tsubasa Kudasai
Songs featured in the anime
Fuwa Fuwa Time (Light and Fluffy)
Fude Pen Boru Pen (Calligraphy Pen Ball Pen)
Curry Nochi Rice
Watashi wa Hotch Kiss (Stapler)
Pure Pure Heart
Sakuragaoku school anthem (lol)
Gohan wa Okazu (sorta recent, doubt it'll be in)
U&I (same as gohan wa okazu)
And now IMAGE SONGS
Guitar ni Kubiddake
Sunday Siesta
Heart Goes Boom
Hello Little Girl
Girly Storm Shissou Stick
Mokujise Happy 100%
Dear my keys Kenban Mahou
Hummingbird
Jajauma Way to Go
Watashi wa Watashi no Michu no Iku
Lovely Sister LOVE
Oui Love Word
Cooly Hotty Tension Hi
Prologue
Maddy Candy
Hell the World
the other death devil songs i can't remember
Let's Go!
Might be more, I'm not sure
note: its not actually a list of songs in the game just ones that are likely to be in there due to them *existing*