Update (much longer than it should be - took two @#$ing days to write):
TL;DR - Even though I was non-plussed about this weekend, it looks like I found the first couple of folks!
First off, I didn't realize that I accidentally booked myself from 4p-2a on Sunday. Whoops.
I also wasn't thinking about it when I did another hour of practice at 12, which turned into a couple hours of bluegrass jamming with my mando player, which turned into "oops, I gotta go" to my 4p jazz session, followed by the 6p one where I met the guys for the project, followed by a 9-2 (half-a**ed) folk-rock jam session, followed by utter collapse, because playing 12 out of 14 hours is exhausting and makes my arms hurt. My arms (and fingers) are still a little tender two days later.
Anyway... Last week, I made contact and scheduled time with a singer that was interested in doing some gypsy jazz. I love me some Django, but I was pretty worried about the odd-ball musicianship required. Spent a day or two working out a couple of patterns and was feeling OK about playing simple stuff and walking over strange VI-IIIb changes. This turned out to be a little too much prep for the situation, 'cause that was just something he said.
I showed up about 15 minutes before call. I didn't realize we were setting up in a recording studio, but it was Sunday night, so no worries. Thought "Hey, we're in a studio, maybe the people will be pro's." That was almost true. I showed up early so I can be set at call time. I guess I'm the only bass player in town that does this, 'cause I was ahead of the front man, and the drummer was 90 seconds behind me. This was a jazzy kind of session, so I brought fakebooks, lead sheets, cables, batteries, etc. I'm glad that I do that; it came up multiple times. I learned (at least the basic changes) the songs that were on the try-out list and listened to them a half-dozen times to get the "feel". I thought that went without saying, but that is apparently not true either.
Cast
Nick the Vox - Trying to break into the local scene with a jazz/blues ensemble concept, but no real "jazz background". Good voice, interesting timbre, motivated, and has extraordinary contacts throughout the local scene (he was the one with the free studio time). Wants a "horn section" but doesn't know about arrangements.
Tim the Fiddle - Interested in getting beyond the bluegrass-folk-country scene that fiddle players are sometimes forced into regardless of preference. He was prepared-ish and pretty talented.
Clancy the Drummer - Professional, professional, professional. Does local shows with a theater company and has previously been a part of a REALLY good big-band in town. When I saw his ragged case full of well-used top end cymbals, I almost jumped for joy. Solid as a metronome, less-is-more fills, no-problem attitude, etc. He was freaking amazing.
Chris the Guitard - Great axe. Consumate noodler. Tin ear. Oblivious to the pocket. "Not great at rhythm" (direct quote). Learns by ear, which is pretty depressing based on his performance. Might know most of the chords, but not nearly all of them. Doesn't do "covers" (btw: for those that don't know, jazz is oftentimes based on standards, which are 500-1000 songs written as a basic melody line and changes that serves as a starting point for improv stuff and band arrangements - in this context, he would classify >50% of the whole genre as covers). I'm not sure if he ever played with a non-rock ensemble before. Certainly didn't sound like it.
Aside: The last couple of weeks, I have realized that if I need to scream changes more than once-through at a guitar player, even if he has a sheet; I just shouldn't be playing with that musician. It is NOT OK to get so lost, at such a high volume, in a three chord song, that the bass player has to physically walk over to pass changes along every time through. On the third song, I plugged a mic into the board so I could stop screaming. I walked over to show him the fretboard. Played quarter note roots for a while. Asked the drummer to smash on the 1s, whereupon he gave me a look that meant "*** is up with that guy" but did it anyhow. It didn't work. Nothing worked.
Nick passed around a setlist that was absolutely my style. It's not precisely what I was thinking in the OP, but awfully, awfully close. I knew 90% of the songs, and had played about 25% professionally before. Rusty or not, once you've played something on stage 30 times, your fingers remember even if your brain doesn't. He picked a couple and we got to work. I had charts for some in my current print library, so I was able to feed the guitar and fiddle.
All of Me is a jazz standard made popular by Sinatra, but recorded by a couple dozen other players. Changes are complicated jazzy ones like Bm7/5- and Adim11+13. I thought, "Hey, what a good idea, we can see where everybody is at musically and Frankie swings so hard that it might take a little juice to keep up." Fiddle guy picked up melody immediately and started doing fills on the second rep. Drummer nailed it. I nailed it. Vocals were shaky, but acceptable for the first time through. Guitard picked up a super-loud fistful of notes that kinda went together and sorta resembled the chord in the song, which threw off the singer. On the second rep, he stopped to screw around with the amp. This was a good thing, 'cause all of a sudden, the vocals got a hundred times better.
The next day, I got a follow-up from Nick, who wants to be the charismatic frontman, equipment provider, and consumate scenester, but not the "music part" of being a BL. He asked for help with musicians, and arrangements, and horn players. We're meeting tonight to talk more, but based on this weekend, I've got a GOOD project!
He also called me talented, prepared, and professional. I said "Thank you" without laughing, which was a giant win for me.
I already have a (fairly talented) trumpet player and possibly a (pretty darn impressive) guitar too, so the group is already in good-ish shape. I'm keeping Sunday's Vox and Drums for sure, probably Fiddle as well. Also keeping 75-80% of the vocalist's set list. The guitard didn't like me due to my bad attitude towards screwing around (don't like it and tell people politely to stop: "Hey, Chef Boyardee, could you quit noodling for like two minutes"), and I didn't like him due to his bad attitude towards musicianship and ensemble rehearsal. He can eat a #$^%.
How the @#$%# am I going to do the horn arrangements? I haven't done a real arrangement in like 10 years. I don't recall being particularly skilled at it back then either. How the !@#$% am I going to find the horn section? Based on the feedback here, Craigslist is almost certainly a horrific venue for those guys.