Once 6/8 makes sense, the rest of the compound family is just "the same idea, more beats."
9/8 — three dotted-quarter beats. A "slip jig" in Irish music; the slow movement of a
Bach sonata. Count "1 2 3 4 5 6 7 8 9".
12/8 — four dotted-quarter beats. The engine of a blues shuffle and a doo-wop ballad;
We Three Kings. Count in four big beats.
Divide the top number by 3 to get the real beat count: 9 ÷ 3 = 3, 12 ÷ 3 = 4.
9/8 — three big beats
120 bpm
Nine eighths, beamed 3 + 3 + 3. Lean on 1, 4 and 7 — the three dotted-quarter beats. Then feel just those three and let the rest flow.
12/8 — four big beats, the shuffle
120 bpm
The 'long–short' shuffle groove: on each of the four beats, a quarter then an eighth. Count in four — 1, 4, 7, 10 — and let each beat swing.
The odd cousin: 3/8
Not every x/8 is compound. 3/8 has just three eighth notes — one beat, felt as three
quick divisions. It's simple triple, the little sibling of 3/4, not a compound metre at
all. The test still works: 3 doesn't divide by 3 into a sensible beat count, so it's simple.
72 bpm
3/8 — one beat a bar, split into three fast divisions. A quick one-in-a-bar feel, like a very fast waltz.
Quick check
Check yourself
1
2
3
4
The usual mistake
Assuming any time signature with 8 on the bottom is compound. 3/8 isn't. And counting 9/8 or
12/8 as nine or twelve beats — it's three and four, with everything else as division.