Think about it more... the jaw harp [jew's harp] doesn't really require
any airflow at all to be played.
I'll bet that you don't play a jaw harp. You won't hear much if there's no
air flow, not to mention that changing air flow direction and making
syllables is how you get beats other than when you strike the twanger. It's
a lot like rhythm harp.
In the sample at the link below, I'm holding my breath for the first and
last four notes. On the stuff in between that, the quarter notes
are the only ones where I strike the twanger, the others are breath changes.
It's just the "Tom, Tom, greedy gut" rhythm, nothing special. There's a
steady cadence on the twanger except for an air strum past the twanger on
the "gone" for a half notes. The low volume on the first and last four beats
is entirely due to breath holding, the strike is unchanged. Actually the is
an increase in volume on beats 3 & 4 is because I let a tiny bit of air
flow. Air flow is absolutely essential for volume, and rhythm technique.