Play a C major chord and a style sounds right. Play an A minor 7 and it still sounds right — same groove, different notes, all in key. That magic has a name: chord-follow, and it’s controlled by a part of the style file called the CASM. This post explains how it works, without the mystery.
The core idea: a pattern plus a rule
When a style is made, each part is recorded once, over a fixed reference chord — for Yamaha, that’s C major 7 (Cmaj7). That recording is the “source pattern.”
The style does not store a version of the pattern for every possible chord. Instead it stores the single Cmaj7 pattern plus a rule for how to transform it when you play something else. That rule set is the CASM.
So when you play F major, the keyboard takes the Cmaj7 pattern and, per the rule, transposes and reshapes it to fit F. One recording, any chord.
Where the rules live: CASM → Ctab / Ctb2
Inside the style, the CASM chunk holds one record per part, describing exactly how that part follows chords:
- In SFF1 styles the record is called Ctab.
- In SFF2 (GE) styles it’s Ctb2, which is richer — it splits the note range into low, middle and high zones, each with its own rule. That’s why SFF2 guitar parts sound so lifelike.
Each record also carries the routing — which recorded channel feeds which of the eight parts — the note-range limits, and a couple of behaviours we’ll get to. The two settings that do the heavy lifting are NTR and NTT.
NTR — how the pattern moves
NTR (Note Transposition Rule) decides the overall strategy for moving the notes:
- Root Transposition — shift the whole pattern by the distance from the source root (C) to the chord you played. Great for melodic and bass lines: the shape stays, it just moves.
- Root Fixed — don’t shift the pattern up and down; instead keep the notes roughly where they are and re-voice them to the new chord. This keeps a chordal part from wandering octaves away. (Play C–E–G and, at F, you get C–F–A — a different inversion, same register.)
- Guitar — a special mode for realistic guitar voicings, so the part behaves like fretted strings rather than a transposed piano.
NTT — which notes it lands on
NTT (Note Transposition Table) decides how individual notes are mapped once NTR has done the big move:
- Bypass — no remapping at all. This is what drums use (a snare must stay a snare, whatever chord you play).
- Melody — maps notes diatonically through the played chord’s scale, so a melodic line stays musical.
- Chord — snaps notes to the tones of the played chord.
- Bass — like Chord, but tuned for bass behaviour.
- Minor / scale tables — variants for minor and modal contexts.
There’s also Bass on, note-range limits (keep a part inside a sensible register), and RTR (retrigger) — what happens to a held note when the chord changes: stop it, shift it, or retrigger it.
The one invariant that proves it’s working
Here’s a useful sanity check that always holds: drum parts use Root Fixed + Bypass, with limits wide open (0–127). Drums must never transpose. If you ever see a style’s drums changing pitch when you change chords, something is wrong with how it was built or decoded.
Why this matters when you edit
If you edit a style and it suddenly sounds “off” on certain chords — a bass note that jumps too high, a chord part that drifts — the cause is almost always in these CASM settings, not in the notes themselves. Understanding NTR/NTT is what separates “I moved some notes” from “I actually fixed the style.”
See it and hear it for yourself
The hard part of all this is that it’s invisible on the keyboard — you can only hear the result. The Quandle Style Editor makes it visible: it reads the CASM to lay out the real parts, exposes the chord-follow settings per part, and — the useful bit — lets you play the style back while you throw different chords at it, in the browser or out to your own keyboard, so you can hear exactly how each part responds before you commit to a change.
It’s the fastest way to build an intuition for chord-follow: change a chord, watch and hear what each part does. And since it runs in your browser, your file is never uploaded and there’s no account to make.
Curious how your favourite style follows chords? Open it in the editor and try a few.