How do jazz musicians learn, hear and think of tunes? They do it the way we all understand, read and speak. In chunks and in links between chunks, not word by word. Even when you put a new chart in front of them for the first time, they don’t read a chord at a time, they read in chunks and links between chunks.
It’s also not surprising that experienced players can do any tune in any key. They’re not geniuses – it’s simply a byproduct of the way they understand the harmony. They’ll know what the “usual” key is, to be sure, but they actually understand the tune in terms of its harmonic movement without reference to any specific key at all. And they’re thinking in Latin…
Here’s roughly what’s going on inside a jazzy head when playing a very common tune:
“A: II V I in major; II V I in relative minor
B: II V I in minor; II V I in major
A: II V I in minor, then optional semitone slips down; II V I in minor”
“A: I, up to bIII, then down by semitones back to I, moving by slabs
B: II V I to I; II V I to bIII; II V back
A: As before
C: II; II V to VI; II V to III, which becomes the start of a III-VI-II-V-I to finish.”
Here’s another one, a bit jazzier but still very common:
“I, then backdoor II V to
I, then II V modulation to
bVI, then II V to V
II V I, then turnaround with every chord tritone subbed and changed to major 7th.”
What about the melody? Well, a fair amount of practice, learning and listening is required along the way, but ultimately if you have the harmonic structure down, a combination of ear training, physical memory and sheer experience takes care of business. Now I’m a bit down on players who “jam the head” – far too often, they’re “creatively embellishing” the tune because they don’t really know it properly. That said, if you know your intervals and the harmony, there’s far less hunting and pecking involved.
ON MY SIGNAL, UNLEASH JAZZ…
There is more nuance to it, of course – for instance, consideration of how long these harmonic chunks last, the fact that certain chords suggest or demand certain alterations, and some more modern tunes aren’t really concocted in this functional way and have to be understood differently. But it really is the way jazz musicians think (when we’re thinking at all). As an improviser you have to be as much a composer as anything else, and that means understanding the harmonic structure of what you’re playing.
So when a jazz musicians sees Abm7 G7alt GbM Eb7alt they’re not reading a chord at a time. They’re thinking: this chunk is in Gb and it’s a II V I VI with a tritone sub on the V.
Knowing your contrafacts helps too. A contrafact is a tune written on the harmony of another one, so for instance, Donna Lee is based on Indiana; Half Nelson and Ladybird are pretty much the same; Ornithology is How High the Moon; Weaver of Dreams is basically another Another You, and so on. Contrafacts are often altered or hybrids, so you’ll often hear a jazzer say something like: “it’s a slightly reharmonised X with a Y bridge.” Even a bit of this knowledge can help – Coltrane’s Lazybird may seem like a challenge, but it cuts out a lot of work if you realise that the bridge is the same as Lover Man.
Roman numeral analysis of harmony may look forbidding, starchy, academic – even pompous at first. But it will completely unlock the way you learn, think and improvise. When someone on the stage is quickly explaining a tune, they won’t be saying things like “Gm7 C7 F Bb, the bridge starts off Bm7 E7 A”, they’ll be saying “two five one four, then the bridge is up a major third…”. And they’ll be thinking in Latin.
Incidentally, classical musical analysis demands that you use lower-case Roman numerals for triads that are minor. Jazzers usually just take it as read that you’ll know when they’re supposed to be minor or major, given the context. We’re lazy, you see. Just like the Romans were whenever they got the chance.