Most musicians massively underuse their mouths, and the ones that use their mouths underuse their fingers. This is very weird and I don't understand it.
The most common instruments I see are probably piano, guitar, drums, and violin. Add in mandolin, bass, accordion, cello, viola, and banjo, and they all have one thing in common: your mouth is completely idle.
Then there are instruments that do use the mouth, but these don't use anywhere near the full capacity of your fingers. A trumpet, baritone, or tuba has just three buttons and a mini slide, and the other hand just sits there. The trombone and harmonica just need to be moved back and forth. The flute, clarinet, sax, and oboe do at least use both your hands, but using all ten fingers to select a single note is terrible. Recorder, tin whistle, and bagpipes are even worse: not only do they require all your fingers, but your mouth isn't doing very much.
This does make sense historically: while your mouth is incredibly versatile, there aren't obvious ways to combine it with a guitar, drum, or violin. And the easiest ways to build a wind instrument all require a lot of fingers so you can spread them out along a tube. But we've had serious electric and electronic instruments for decades: why is it still uncommon to see people using their mouth's incredible ability to modulate sound? Some people sing and play at the same time, which is great, but probably less than half of musicians?
I wrote about this a bit in 2019 in Where are the new Instruments?:
Breath controllers, which sense breath pressure and make it available as one input to a synthesizer, have been around for decades, and are old enough to have been assigned CC-2 in MIDI. Lots of people have tried them, with some impressive results, and there's no risk of being tied to a vendor since they're so simple. But even though they would allow anyone playing keyboard to add a new dimension to their playing, musicians are sufficiently uninterested that Yamaha discontinued their BC line in 2011. The electronic instruments that have taken off live are mostly just keyboard and maybe drums. There are so many fantastically creative people in the music industry, but in the 80s innovation here seems to have stopped. Why aren't people coming up with creative new ways of modulating the sound as you make it?
Since then I've been using the breath controller more live, and have started playing with a talk box too. Which has the same mystery: anyone can attach a talk box to any electric or electronic instrument, and get far more control over their tone and dynamics. But they mostly don't. It can't just be that having a tube coming out of your mouth just looks too weird since people play wind instruments. With how innovative people are in other aspects of music it feels really weird to me to see so little exploration here. Why?
(There's also an instrument in this category that could have been built any time in the last ~500y: talkbox bagpipes. While the mouth-blown pipes are probably most familiar, all the mouth is doing is putting air into a bag. Bellows pipes replace this with an arm-operated pump. This opens up an opportunity to point the drones into your mouth so you can manipulate the sound of your accompaniment, turning the drones from a continuous, well, drone, into something lively and danceable. Or, at least, it should. As far as I know no one has built these, and my attempts to convince my bagpipe-maker cousin to work on this haven't been successful.)
There are many kinds of expressive controllers, they've been around for decades. They didn't catch on. Not sure we can answer why: failure to catch on is the default, it doesn't demand an explanation. The interesting question is why other things succeeded in the meantime, like keyboards with knobs, or drum machines, or turntables. Why they led to impactful music, while a lot of more advanced stuff didn't. It seems the reasons are cultural, and different every time.
What this means practically is, there's no guaranteed path. You can try to make an expressive controller, but there are already lots, so not sure the point. You can buy one online and try making impactful music with it, so far nobody succeeded but maybe you will. Or you can reexamine the hypothesis that expressive controllers are what's lacking in music (for me personally it's well and truly refuted), and search for something else. Up to you.
Edit: this HN comment (not by me) is about a similar topic, not specifically expressive controllers but generally the mystery of which musical instruments catch on and which don't.
How does the kazookeylele rate for good combined hand+mouth usage?
It's a funny video, but attaching the kazoo to the ukulele doesn't actually do anything...
Bagpipe lung may be an issue with that last. I could see where the bellows design should at least mitigate the risk, though.
Off the top of my head the EWI uses breath to operate an electronic instrument. Unfortunately, I don't know any EWI players so I couldn't tell you how much control it allows.
Good point! I wouldn't expect this to be a problem with a bellows instrument, though, since that doesn't involve sending humid lung-air into the bag? Probably also doesn't explain why it wasn't invented centuries ago?
Generally they have two mouth sensors: breath pressure and bite pressure. This is quite a bit less information than, say, a sax/clarinet gets from the player's mouth. From an input perspective they're essentially keyboard+breath+bite with much more limiting fingering.
Well, most musicians also massively underuse their feet; the only instrument traditionally requiring your feet to do very complicated things is the organ.
I still don't find this particularly surprising, since the average musician usually hasn't the goal of maximizing the musical information rate. Staying idle with your feet or mouth is obviously easier than the alternative (any pianist who tried to play organ or piano+lyrics can confirm). Also, the traditional repertoire for any given instrument is tied to the intended use.
I would also endorse a "musicians massively underuse their feet" position. https://www.jefftk.com/p/introduction-to-heel-toe-drumming