I hear bits and pieces of Heart's "Crazy Over You" combined with the show-tune "What I Did For Love." from a Chorus Line in a couple of the compositions.
@Hosfac: You remember the 90's song "I Wanna Be There?" Sims also play that song on their guitar, sometimes with the "Layla"/"Losing My Religion" Medley. I think the theme song to the hit TV show "Friends" "I'll Be There For You" is included along that bit sometimes as well.
@Pam: I think EA designed the Sims to play bits and pieces of these famous songs off key, to avoid copyright issues, and to get people like us guessing. I think EA
wants us to guess the bits and pieces of the songs our Sims are playing on their instruments, in an off key, scattered fashion. If the Sim were to learn to play Layla on the piano, for one, Eric Clapton would be suing EA, and another thing, it would take the fun out of guessing, what bits and pieces of the songs Sims are playing on their instruments.
@Grimsoul: "The Entertainer" I believe, is a traditional piece, along with "Twinkle Twinkle Little Star". It's the most frequently played tune on the ice cream truck, you know. So therefore, they wouldn't really have copyright issues. Also, you remember the song "Faithfully" by Journey? I heard the piano part mimicked, slightly off key. I have heard them also mimic the really long instrumental of the original version of "Layla."
Edit: Sometimes, when you set the speed to "Ultra Speed," you will hear a real life song played on the guitar. Skip over to
0:16 and again at 1:55 and you will hear the chorus of the song Layla. Pretty cool huh?