This from the unit history of the 4th Squadron, 7th Cavalry:

In 1867, one of Custer's first official acts with the Seventh Cavalry was to organize a regimental band. The reason that "GarryOwen" was adopted as the regimental song, as the story goes - one of the Irish "melting pot" troopers of the 7th Cavalry, under the influence of "spirits", was singing the song. By chance Custer heard the melody, liked the cadence, and soon began to hum the tune himself. The tune has a lively beat, that accentuates the cadence of marching horses. Soon the tune was played so often that the 7th Cavalry became known as the "GarryOwen" Regiment. GarryOwen eventually became the official song of the 1st Cavalry Division at Fort Hood, Texas in 1981.

I knew as the song played by the 3rd Squardron's pipe band in 1964-65 where it was the divisional screening force for the 3rd Infantry (Marne) Division

Garry Owen!

See: http://www.metronet.com/~harryb/1st_team/7th_rgmt/ and http://www-2id.korea.army.mil/Major_Subordinate_Commands/Aviation%20BDE/4-7cav/HISTORY.HTM