MIDI Progress

[Steve Schulteis]

Other things (like publishing a tune book!) have kept me busy for a while, but recently I've been giving attention to my MIDI build again. This time I'm using photointerrupters for the buttons and a DIY string pot to measure the bellows. I still need to dial in the bellows sensitivity, and I have a long list of other improvements for the next version, but overall I'm very happy with where this one is at. It's a lot closer to what I'm aiming for, and I feel like I know where to look next to get the rest of the way there.

 

The project files for this are a total scattered mess, so I don't plan on publishing them. That said, a big part of what I intend for the next iteration is to release complete designs (schematics, PCBs, 3d models, source code, etc.) under an appropriate open source license. In the meantime, I'm happy to answer any questions about the current build.

 

I'm planning to bring the latest version of this with me to Old Pal, so you can try it in person if you're there!

 

 

[Gregor Markič]

I love this. The sound isn't bad and the looks are 100% realistic.

[Steve Schulteis]

2 hours ago, Gregor Markič said:

I love this. The sound isn't bad and the looks are 100% realistic.

 

Thanks!

 

The sound is produced with the sound font linked in Don Taylor's signature on this forum.

[Steve Schulteis]

[JimR]

That looks very nice!

 

[Don Taylor]

On 3/15/2025 at 9:57 PM, Steve Schulteis said:

In the meantime, I'm happy to answer any questions about the current build.

Are you doing your own 3d printing or getting it done by a fabrication shop?

 

What microcontroller(s) are you using nowadays?

 

Can explain more about your button mechanism, particularly the physical part and maybe show some pictures?

 

Do you think that you will be able to mute the button clicking?

 

[Steve Schulteis]

2 hours ago, Don Taylor said:

Are you doing your own 3d printing or getting it done by a fabrication shop?

 

Doing it myself.

 

 

 

2 hours ago, Don Taylor said:

What microcontroller(s) are you using nowadays?

 

I've currently got a whole Raspberry Pi Pico on each side, mounted on a custom PCB. For future iterations, I plan to use the RP2040 directly on a custom board, which I'll pay to have populated rather than doing it myself.

 

 

 

2 hours ago, Don Taylor said:

Can explain more about your button mechanism, particularly the physical part and maybe show some pictures?

 

I'm using photo-interrupters to sense buttons. I'll probably switch to hall-effect sensors in the next iteration (mostly for production reasons). The physical mechanism should be about the same, though.

 

The buttons themselves use standard keyswitch springs, which are currently cheap and abundant thanks to the mechanical keyboard market. A bit of brass wire runs through the spring and its housing, connecting the button cap to the optical gate and helping establish the path of travel. The button cap fits through a nylon bushing, which also helps keep the button aligned and prevents the layer lines of two 3d-printed parts grinding against each other.

 

Here are some pictures of trial pieces I printed to test the button mechanism design. In the actual instrument there's just one spring housing that accommodates all the buttons, and the bushings fit directly into the outer shell.

 

 

Here's a back view of a couple different iterations of the outer shell (and parts of the assembly that go inside it).

 

 

 

2 hours ago, Don Taylor said:

Do you think that you will be able to mute the button clicking?

 

Absolutely. There's currently no padding at all in the button mechanism, so it's plastic on plastic, which makes an awful racket. I intend to add something to dampen this noise in future versions. The reasons I didn't do that for this one are 1) I needed to see if I could leave the padding out to keep costs down in the eventual production version, and 2) I wanted to have it done in time for Old Pal, and there were more important details to focus on first.

 

Of course for anyone who's just concerned with recording, the button noise doesn't affect the MIDI signal in any way.

 

Thanks for all the great questions, Don!

Edited March 24 by Steve Schulteis

[SIMON GABRIELOW]

Can the MIDI concertina have different sound effects ie: violin sound, clarinet sound, etc like an electronic keyboard? or the normal reed sound only?

Edited March 25 by SIMON GABRIELOW

[Richard Mellish]

4 hours ago, SIMON GABRIELOW said:

Can the MIDI concertina have different sound effects ie: violin sound, clarinet sound, etc like an electronic keyboard? or the normal reed sound only?

For me, the very reason for wanting to build a MIDI concertina was to have alternative sounds available from a familiar configuration of buttons (which one might or might not choose to call a "keyboard"). I would expect any MIDI concertina, including Steve's design, to likewise offer a range of sounds.

[Paul_Hardy]

Yes, any Midi instrument by definition requires a synthesizer component, to produce sounds in response to the button up/down and pressure information. My midi concertina (https://pghardy.net/concertina/lachenal_30566_midi/lachenal_30566_midi.html) uses an iPad app as synthesiser, and can access a vast range of realistic sampled instruments, as well as abstract synthetic sounds.

 

This weekend, I had it at the WCCP weekend at Halsway in Somerset (along with another 70 or so concertina players), and in the evening session played Boolavogue using primarily cello sound, but with added celeste sound to emphasize note starts. The tina can drive three Midi channels, so you can have up to three different instrumental sounds (at different octaves) happening when you press a key.

 

Incidentally the usual name for the human interface part (with keys, buttons or other items) of a Midi chain is described as a "Midi control surface".

[Steve Schulteis]

Yup, just like Paul, I'm using an external synth - the MIDI concertina is just a (USB) controller. So it can make any sound your chosen synth provides.

[Tiposx]

That is very clever engineering. I should imagine that the instruments would be useful for quieter practice. I also like the idea of recycling old Lachenals etc that have poorly reeds, like the one in Paul Harry’s link.

[RAc]

well, yes, any synthesizer can produce almost any sound, given preprovisioned sound fonts. The remaining question, however, is: How to switch between sounds?

 

I also use an RPi (running fluidsynth with the same font that Steve uses) as the synthesizer on my MIDI crane, and it would be max an hour's work to add, say, a dozen other sound fonts to choose from.

 

Yet the interesting question is how to select the font. One would have to come up with some kind of "Midi control surface" (thx Paul) to switch between fonts - eg on my Crane I have a few buttons without a sound mapped to it, so it would be an obvious choice to use those - for example one short press concertina, two violin and so on. Or use any combination of three buttons after a "mode select" button to select one of eight instruments. Or anything else. Then program that scheme into your button processor (in my case an Arduino) to generate the midi select instrument commands from it.

 

So theoretically almost everything can be done, but it needs to be implemented. For my project, I won't bother because I use it for practicing, not music making, so one font (that as a bonus even sounds like a concertina) will be doing perfectly ok.   

[Paul_Hardy]

For my midi tina described above, there is one additional button called 'Program' at bottom left. You press and hold this in a chord of three -  firstly one of the above three buttons to say which channel, then any of the remaining standard buttons to say a function. Different areas of buttons have different functions - the white buttons on the left side are volume, the black buttons select octave or transposition, while all the buttons on the right hand side select a new instrumental sound from a set of favourites. See 

 

You can also select a different instrumental voice (from a much bigger selection) in the synthesizer on the iPad, but that means letting go of the concertina.

Edited March 25 by Paul_Hardy
Clarity

[Don Taylor]

Midi players play sampled sounds stored inside sound font files.  There does not have to be a sample for every note because Polyphone (see below) will interpolate between samples to give you any missing notes.

 

You could create your own custom instrument, perhaps based upon sound samples from your own concertina.

 

I used the Polyphone sound font editor to tweak Phil Taylor's original sound font, but you could sample your own sounds and create a new sound font.  Polyphone is not difficult to use, getting a clean set of samples is more work than editting them into a sound font.  Polyphone is a free, open-source program.

 

Phil's sound font is based on very few samples and was especially short of samples for the higher notes and yet it still sounds pretty good to me.

Edited March 26 by Don Taylor
Corrected to say that Polyphone interpolates between samples to make up for missing notes.