Passed on by David Beaver, a Bizarro from 2007:
One pun in the cartoon proper, another in the title.
The speaker’s words in the cartoon play on two senses of tone: (1) musical quality (appropriate for a choir), (2) ‘modulation of the voice expressing a particular feeling or mood’ (NOAD2), as in tone of voice (the usual sense in “I don’t like your tone”).
The title plays on the movie title Shootout at the OK Corral, with chorale (the choir context again) for corral. This is a perfect pun for me, but some have /o/ rather than /ǝ/ in the first syllable of chorale, and some have /a/ rather than /æ/ in the second syllable of that word.
Both puns juxtapose the choir world to the cowboy world.