"Song in My Heart" is an original song performed by The Chipettes featuring Simon Seville and Theodore Seville in the ALVINNN!!! and The Chipmunks episode The Sub and has yet to be released as part of an Alvin and the Chipmunks album.
Lyrics
The Chipettes:
I've got a song in my heart
I've got music and rhythm
Sing forever and ever
Like a melody and I got harmony
I've got a song in my heart
I know that I'll never lose it
'Cause everywhere I hear music
And that's just exactly how life ought to be