Catharsis is an Amy Cann fiddle tune that's exciting, difficult, and overplayed. There are a zillion recordings of it, but here's one from a contra dance:
It's in Gm, dark and brooding. But what if it were major instead? A long time ago, when I still played guitar, I figured out a set of chords in Bb:
|: Bbmaj7 / Cm7 / Dm7 / Cm7 F9add11 :|
Bbmaj7 / Cm7 / Dm7 / G9add11 /
Cm7 F9add11 Dm7 G9add11
Cm7 F9add11 Bbmaj7 Cm7F9add11
The fiddles still play the same notes, but with the chords you interpret the tune as being in Bb instead of Gm.
It's super cheesy, and combined with a tune as overexposed as Catharsis I wouldn't normally play it at a dance, but what about an open band? When you have a group of musicians who are just together for the evening, cheesy and overdone is not a downside!
Except, how would you get an open band to play those chords? Say "F9add11" to a folk guitarist (including me—I had to look up the names of these chords for this post) and they won't know what to do. It turns out, however, that these chords can each be pretty well approximated as a combination of a bass note and a well-known chord. For example, Bbmaj7 is Bb, D, F, and A. If the bass player or piano left hand plays Bb, that leaves D, F, and A for higher-pitched rhythm instruments like guitar. And D, F, and A just makes Dm, which your guitar players can do. So:
| chord | bass | treble |
|---|---|---|
| Bbmaj7 | Bb | Dm |
| Cm7 | C | Eb |
| Dm7 | D | F |
| F9add11 | F | Cm |
| G9add11 | G | Dm |
Which gives us:
|: Dm / Eb / F / Eb Cm :| Dm / Eb / F / Dm / Eb Cm F Dm Eb Cm Dm EbCm
It's still not a great fit for an open band: you need fiddlers who are comfortable with a tune this hard, and while the chords are now closer to the folk repertoire they're flatter than ideal. But while I haven't tried this with a real group of musicians, with the right ones I do think it should work!