I don't always rehearse my music / but when I do, it's always in first service
A Dos Equis Man meme.
Dos Equis Man is Jonathan Goldsmith as the suave, bearded Most Interesting Man in the World from the Dos Equis beer ads. The captions use his line's shape: "I don't always X, but when I do, I Y." It's the meme for confessing habits with legendary confidence.