Ringing barrel refers to shooting a 55-gallon steel drum and having it sound like a church bell.
By hanging the steel drums from different length chains and springs and having different materials and different amounts of those materials in the drums the notes of the drums (bells) can be changed.
By combining different drums at different distances and different guns and different ammo you can play Dixie.
Yankees can play The Battle Hymn of the Republic, but they'll likely be off-key.
Of course in Texas they will play either The Yellow Rose of Texas or The Red River Valley. But it takes practice.