"Is that tune crooked?" You have to think about that because you can't play crooked tunes for dances.
To find out if a tune is crooked, count it out. Is it a thirty-two bar reel? A/A/B/B? Each part, eight bars?
For a while, I played a version of Arkansas Traveller , called Bill Clinton, that drops a beat from the A part and added one to the B part -- it's crooked, but gets away safe by the end. It's a reel. It's thirty-two bars. The parts aren't eight bars apiece, so it's no good for contras.
Even if you can't play them there, you can probably play them for cloggers. If you can tap your foot to it, so can they. The only tune I play that I can't tap my foot to is called Cotton-Eyed Joe, learned off of a Gypsy Gyppos album, and I saw Dan Peyton rise to the challenge once and even clog to it.
The tune is, by the way, unrelated to either the yee-haw, Cotton-Eyed Joe of line-dance fame or any other Cotton-Eyed Joe I've ever played. Not a shock. Scott Mathis says he has a tape, somewhere, full of nothing but tunes named Cotton-Eyed Joe, all unrelated.
When else might you ask, "Is that tune crooked?"
The question seems to lie outside the universe of discussion for waltzes, but, there are even crooked waltzes of a sort: fun to play, but annoying to dance to. Too slow and too fast are obvious problems, but some waltzes have an odd number of measures, so start you off on the wrong foot every other time through. I've heard The Tombigbee Waltz played this way. Musicians think, "Cool waltz." Dancers think, "Eeew."
I've heard these excused by musicians as "American waltzes," so maybe they'd work if the dancers knew what was coming and treated them as a novelty. Instead, they just grumble on the dance floor to one another, "This band is doing something wrong."
Square them off, or save them for the parking lot.
Jigs? I've never heard a crooked jig. Slip jigs, like The Butterfly, Kid on the Mountain, or Rocky Road to Dublin, aren't crooked, they're just a different animal. They're in 9/8, so instead of being made up of measures of "higglty-pigglty," they're made of "how can I ever play this?" They're not crooked, but only your Irish step-dancing friends will put up with them.
Three- or four- or five-part tunes? I've occasionally heard them called crooked, but if they have 8-bar parts, I don't think of them that way. They'll work fine for for Southern squares and for long-lines dances, like the Virginia Reel, but ask the caller if you can play them first. When I was first calling, I remember struggling when the band started a jig. I'd only ever called to reels.
There are, however, three-part, thirty-two bar tunes that aren't even crooked. The Rags, which I learned from John Kirk, when he was crashing on my couch, is A/A/B/B/C/C, but the B & C parts are each half-length, and it makes a fine contradance tune.
Once in a great while, a good caller will ask you for a three-part, 48-bar tune to fit a dance. You actually probably know a few of these, so put a couple on your list that you can pull out without panicking. Being able to start one in each of several keys can save the fiddler and banjo player from having to re-tune. Little Billy Wilson, the three-part Ragtime Annie (D), Bull at the Wagon (A), Texas Gals (C), Cumberland Gap (various keys), Old Melinda (A, in calico tuning) all work fine.
Finally, there are otherwise straight tunes, like Brasstown, that'll give callers fits.
