"Alvin's Harmonica" is a song from the fictional musical group, Alvin and the Chipmunks, which also features additional vocals by Ross Bagdasarian, Sr. who plays David Seville in the song. The song was released as the second single from the group's debut album, Let's All Sing with the Chipmunks in 1958. Like "Witch Doctor" and "The Chipmunk Song", it was adapted as one of the musical segments featured in The Alvin Show.

In the song, Alvin is playing his harmonica, when David Seville orders Alvin to stop playing that instrument and sing with the Chipmunks. When Alvin does not answer David's question, whether Alvin is ready to sing, David screams "ALVIN!!!", forcing Alvin to sing with the Chipmunks. When Alvin, in the song, mentions that he only wants to play his harmonica, David repeatedly scolds him, and orders him to sing again.

Finally, David tells Alvin to make a fool of himself by playing the harmonica, resulting in a rhythm change from a slow 2/4 beat to a "CHA CHA CHA" beat, in which the Chipmunks repeatedly intone "CHA CHA CHA". David angrily scolds Alvin and Chipmunks for changing the innocent rhythm to a CHA CHA CHA beat, getting the people to dance. David screams at Alvin as the song ends. ("ALVIN!!!). Alvin became identified with his harmonica on a Christmas song called "Wonderful Day", from the Chipmunks second Christmas album, in which Alvin received a harmonica to and from himself. ("From me, to me".) Alvin plays the song in a wrong key as the song ends, with David Seville scolding Alvin.

A photo of Alvin with his Harmonica is featured on the album cover of 1964's The Chipmunks Sing the Beatles Hits.

After the group's previous single, "The Chipmunk Song", reached No. 1 on the charts, it was hoped that "Alvin's Harmonica" would reach the Top Ten. The single peaked at No. 3 on Billboard's Pop Singles Chart, becoming the group's second consecutive (and final) Top 10 single on the charts. Since the song was also credited to David Seville by Billboard, the song became his third consecutive Top 10 single on the charts, although it was his first to not reach No. 1.

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