A Fan Fic example is found in the Symphony of the Sword arcs of Undocumented Features. The main character has a rock band that plays a cover of Rockin' in the Free World during a big, onesided space battle, broadcasting their music over the bad guy's comm frequencies. Another arc of the same setting has a group of mercenaries who use a similar tactic that they call the "Goldfish Warning".
Subverted in With Strings Attached; though the entire book is about The Beatles, they play music just a few times, with only the effects one would expect from music on Earth. They even sneer a bit at the notion that their music might be magical.
Douglas Sangnoir of Robert Schroeck's Drunkard's Walk saga gains various magic powers from different songs, usually lasting as long as the song does: Billy Joel's "We Didn't Start The Fire" lets him (and anyone else in the vicinity) relive the second half of his world's twentieth century; "Konya Wa Hurricane" from Bubblegum Crisis, unsurprisingly, lets him summon and control a powerful cyclonic storm; and "I'm a Pioneer" from Tenchi Muyo! makes him impervious to vacuum and capable of superluminal flight.
In L's Rock Band Light Yagami picks up a "Death Note" as in a magic Shinigami guitar that grants Godlike powers.
In The Cadanceverse , Burning Sun and Nightmare Moon are defeated by playing Voltaire's "Riding a Black Unicorn..." at them with Elements of Harmony-infused instruments. A Golem is also defeated by singing Eye of the Tiger while casting spells at it.