I probably don't envision it the same way most people who played through the adventures did, because while I love classical music soundtracks for fantasy, I know common folk didn't play that stuff. I'm from southeast Texas, and in February 2007 when I was editing the adventure, I took a trip to New Orleans during Mardi Gras season, and I guess I had a different musical palette in mind.
I recall deciding that Gate Pass's traditional music had a sound reminiscent of American delta blues.
A modern example:
Or to be a bit more traditional:
Something like ten years ago we published half of a War of the Burning Sky novel, which went through the end of adventure 2. This beat (starts at 2:35) is basically the structure I used for a song that Rantle sings in that novelization, though his song had more lines in each stanza before going to the refrain.
While the Innenotdarasne Elves were mostly all dead by the time the campaign saga starts, I envisioned their music as being along the spectrum of bluegrass...
... to Christian revival music. You know, those long rapturous melodies that take their time (because, well, they're elves and they have time to spare).
And both types of music would have been influenced by the music of the local fey. Which, to use real world music as a baseline, would mean going back to field hollers and the work songs of enslaved people. Which, well, sure have about the same naughty word situation inspiring them as the Song of Forms did.
Here's an excerpt of how I described the song in the novelization.
The song floated eerily above the roar of the forest fire, and though Rantle could not understand the words, he grasped its meaning clearly. Its strangely familiar rhythm brimmed with loss and longing and a memory of beauty which its singers would not abandon, no matter how thickly death surrounded them.
Though he was sure it was just the shimmer of the fire’s heat, the trees appeared to dance with the song’s rhythm. When the music swelled, the flames dimmed, but always an oppressive weariness would creep into the singer’s voices, and again ash and cinders would howl on the wind.
He kept low as he crawled to a hill which overlooked the lake, and he struggled to discern the different singers by their voices and their roles in the song. A core group of at least four, three men and a woman, held the song steady, though other singers occasionally joined from scattered directions around the shore. Two of the men would sing a repeating chorus, while the third man’s deeper voice rose above them in counterpoint, wavering between pride and fear, before finally dropping to a sorrowful drone.
But then, through the despair would rise the woman’s voice, haunting and inspiring, calling out and uplifting the other singers.
The song went through two verses as Rantle snuck forward, and would continue through several more as he and Kathor observed, but as far as he could tell it never repeated fully. Every time he heard the woman’s piercing voice, he could not help but feel weak at the beauty of it.
Take that, and add words of a magic incantation, and you've got the Song of Forms.
But hey, death of the author. If you envision it differently, go for however makes sense to you. But I would encourage looking at sorts of songs people would sing while working: a regular form, with a main singer doing call and response to keep people focused on a tedious task while also taking their minds off how tedious it is.
Maybe consider sea shanties:
Copy of 35 Sea Shanties (57-36 full track) - AC4 Black Flag In Game Soundtrack
Or wool waulking songs (though this is probably too happy and fast):
Wool Waulking Songs
Thanks for asking this question. It got me to put down in text something that previously had only really been bouncing around my head.