This is a topic which really interests me, as I’ve been playing in various ITM groups for the last 30 years in which we’ve tried our hand at creating sets/medleys, and I’ve always taken note of which sets/medleys that I hear others play really “work” for me.
Many of the tune combinations that ITM players habitually play come from old Michael Coleman recordings etc and many don’t seem to make much sense to me personally.
At least two approaches come to mind, as how to go about building sets:
1) pick tunes in keys which create an overall progression that works
2) pick tunes that melodically flow from one to another
For #1, one thinks of the set as a total composition. There are formulaic key changes which nearly always work regardless of which specific tunes are used.
For one such formula, you’ll note how often, in sets, a tune change involves jumping up one note, such as D major/mixolydian to E dorian or G major to A dorian/mixolydian. This rise is somehow inherently exciting and is very common in pop music as well.
A three-tune formula which usually works (almost regardless of which specific tunes are plugged into it) is D maj/mix > E dor > G maj. The tonic continues the rise as you see.
The tunes in such sets need not melodically flow from one to another; indeed there can be a break or silence at a tune juncture.
An example of this might be The Cameronian > Morning Dew > Sally Gardens.
For #2, one is not thinking about the overarching harmonic structure but finding a tune which just happens to sound great coming from another tune melodically.
For example a tune might end on high G and it sounds great to go to a tune that starts on high E (an F# being inserted to smooth it out).
Sometimes you have to play the end phrase of a tune over and over, exploring how to tranisition into various other tunes, until you hit upon something that really works.
For example we play Bunker Hill and it took quite a bit of trying to find a tune that works well in front of it, as Bunker Hill has pickup notes C A and we wanted to find a tune that ended on middle D on the beat before so that we could get those pickup notes in, to get a nice D C A descending thing going into the first beat of Bunker Hill. A Micho Russell reel in D ended up working best.
Sometimes putting together melodies that seem to want to go together creates a set that really doesn’t make much harmonic sense but sounds cool anyway.
I put together The Banner > Sport > Hag with the Money and I just love the “organic” way Sport flows into Hag with the Money, so much so that people are not aware that the tune has changed sometimes. But now the C#s are Cnats and the harmonic structure has changed.
This leads into an intesting thing for me: the different way that Irish players and the old Cape Breton players approached sets. Irish players tend to like key changes so that the different tunes in a set would have different tonics, or in some cases Irish players like to play tunes back-to-back in identical keys with no harmonic shift whatsoever. Many of the old Cape Breton fiddlers would construct sets all in the same key but shifting the mode, taking away sharps as it were, for example
A major > A mixolydian > A dorian.
Interested in this, I put together such a set, of Irish tunes, for my ITM band The Linen Cap > The High Reel > (an A dorian reel I wrote). Plop nearly any traditional reel in A dorian into the final slot to hear how that approach to building a set works. It’s amazingly effective, after the ear gets used to the sound of the Major mode, how that first G natural you hit when you go into the second tune is. Then likewise when C natural appears in the last tune.