The Battle of Gal-Mok was a Klingon opera composed by Kovikh in the third century of Kahless (the late 16th century or early 17th century by Earth dating).
In 2376, a Benzite theater company performed The Battle of Gal-Mok at Ty'Gokor, for an audience of Klingon dignitaries. Their reactions were not positive. (KE novel: A Burning House)