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Electronic (Midi) Concertina - Current Options?

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#37 conzertino

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Posted 24 April 2016 - 09:05 AM

No, it is ordinary foam! I'm still looking for very soft foam, that will actually bend and expand better than the stuff I'm using....

 

I'm using two tubes / hoses, which slide within each other inside the foam-block. There is a magnet in the inner tube and an analog hall-sensor on the outer one. One could also use a magnet within a coil. Displacement of a few mm either way can thus be evaluated...

 

Robert


Edited by conzertino, 24 April 2016 - 09:07 AM.


#38 JimMacArthur

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Posted 24 April 2016 - 05:59 PM

Thanks for the BLE info, Robert.  That really helps me prune the decision tree.

 

My status report:

 

Phone 2016-04-24 028.jpg

 

 

Hardware is finished.  Software barely started.  At the moment, it plays, but with simple wavetable synthesis.  I'm hoping that I left enough firepower to do a decent synthesis job.

 

Robert, I also went with a telephone coil cord to attach the two halves of the concertina, but I went with CAN instead of I2C, mostly because I didn't think to use I2C.  The keys use inductive sensors -- those coils on the circuit board in the foreground sense metal washers at the ends of the plastic keys.  This approach has a slightly lower material cost than magnets and Hall switches, but at the expense of assembly time and processor overhead.

 

The white rectangular block in the upper left concertina is a 1.75AH LiPo battery.  It supplies >>2 hours of play time, which I think is a good compromise for me, considering that I've never played for two solid hours in my life.  And if the battery runs low, you can always plug in.

 

But mostly I wanted to show you the OLED in the upper right.  These displays are crisp, eye-poppingly bright, and not all that expensive.  They do consume current, but considering how small batteries are getting, it seems a reasonable compromise.

 



#39 Don Taylor

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Posted 24 April 2016 - 07:39 PM

I'm using two tubes / hoses, which slide within each other inside the foam-block. There is a magnet in the inner tube and an analog hall-sensor on the outer one. One could also use a magnet within a coil. Displacement of a few mm either way can thus be evaluated...

Robert

Very interesting idea. Do you measure the distance travelled in the last sample period and then set the volume proportionally?

Edited by Don Taylor, 24 April 2016 - 08:44 PM.


#40 conzertino

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Posted 25 April 2016 - 02:26 AM

Jim, that is amazing work! One can tell that you are a professional! 

 

I was looking for a low-cost and simple approach. That's all it takes:

 

Midi5.JPG

 

However I have to start all over again. The switching characteristic of a digital hall-sensor is not accurate enough for a perfect touch-feeling.

 

A traditional concertina will start to sound as soon as you press a key a little bit. A digital hall-sensor will require a certain hysteresis.

 

I found inexpensive ( less than 20 cent! ) analog hall-sensors in China and cheap I2C 10 analog-input-ICs. They output a voltage proportional to the distance of a magnet in the vicinity. So on my latest project I will be able to program the exact switching positions - and in the long run be touch sensitive at very little extra cost.

 

But I can keep using the keys from my older projects, as the actual touch is ok.

 

I wish I could use SMDs... This would make mass-production very simple!!

 

 

 

Don, I'm not interested in the distance travelled as I am not using up air, but in the absolute deviation from the center position: push or pull harder = lounder! The foam acts just like a spring, not a set of bellows... The existing midi-instruments with bellows do not measure the air used up but the internal pressure! As bellows are usually not perfectly air-tight, the bellows on those instruments move a bit while being played...


Edited by conzertino, 25 April 2016 - 02:41 AM.


#41 JimMacArthur

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Posted 25 April 2016 - 04:48 AM

Robert, I think that your approach is closer to what Bruce is looking for.  My approach will never result in a low-cost instrument.  Your use of foam, both for buttons and bellows replacement, is particularly interesting.  I never would have though that foam would have a fast enough action.  Then again, there are some new foams arriving on the market that might do the job even better.  I will investigate.

 

Re analog Hall effect sensors, I totally agree that it would solve many problems with key travel sensing.  Analog Hall sensor prices have plummeted in recent years.

 

Re SMDs, they're not so bad, once you get used to them.  I would be happy to design a circuit board to your specs (that goes for all readers) but much less happy about shipping things to Germany.  I have blown entire days filling out customs forms.



#42 Don Taylor

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Posted 25 April 2016 - 07:44 AM

Robert

So your bellows replacement would not behave quite the same way as a traditional bellows.

As I read your reply, your bellows would function more like a volume control slider whereas in regular bellows it is velocity (ultimately air velocity through the reeds) that controls volume, not distance from a fixed mid-point.

Perhaps measuring distance travelled on a fixed poll and adjusting the volume proportionally would be a decent proxy for velocity.

Designing a cheap replacement for bellows is tricky, but essential to making a low cost miditina. I have some load cells to try, the same as are used in digital kitchen weigh scales, but here the result is that the bellows respond as if they have infinite travel - which might be a good thing. But they also feel rather dead as there is no appreciable movement when you press or pull them. Pressure may not be a good proxy for velocity either. Maybe some foam bumpers would help.

#43 conzertino

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Posted 25 April 2016 - 11:45 AM

Jim and Don, thanks for your thoughts...

 

Today I thought along the lines as to design a flexible solution:

 

"Mass"-produce two ends with with spiral-cable and offer vaious options: traditional bellows, some kind of flexible foam / spring or fixed ( at a slight angle ). They could even be pre-programmed, so that one could switch to another option with a DIL-switch!?

 

I beleive that a 40 key ES with the size of a Stagi mini ( like mine ) is probably the best universal option for an English system!? Don't forget: it is easy to transpose!

 

A good way - specially for anglos - would be, to find a maker that supports the midi option ( swap reed-pans against mini-pans ) for new instruments.

 

I hardly ever use my pressure-control anyway ( is is not working perfectly yet ;-). And why do anglos need dynamics -_-

 

Unfortunatly the expensive item in the job - the printed ciruit-board - has to be redesigned for each model or system...



#44 Don Taylor

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Posted 25 April 2016 - 06:08 PM

I think that Jody might have something to say about the need for dynamics on Anglos...

#45 Jody Kruskal

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Posted 26 April 2016 - 01:07 AM

Why sure, Don. I have a lot to say on the subject.

 

I've been reading this topic from time to time even though I only understand every other word.

 

Please - dynamic control should not be an after-thought but central to your thinking, planning, building and coding.

 

I see no reason why a midi concertina, Anglo or otherwise could not have the feel and dynamic range of a real instrument, even a fine instrument. This matter of a very fine and quick response to dynamic changes would be key to making a pleasant playing experience for anyone, regardless of system be it Anglo, English or Duet... IMHO.

 

In general, the better the concertina, the softer you can play. My Bastari (inexpensive Italian beginners model Anglo) really only wants to play loud. Trying to tame those honking sounds takes a lot of work because when you get quiet, the notes just stop sounding way too soon (and also at an uneven rate). Playing with sensitivity is crude. On such an instrument, playing quietly takes more work than playing loudly. Don't build one like this.

 

My Jefferies (top of the line Anglo) plays like butter. The merest hint of a bellows change in pressure is instantly transmitted to the reeds from a scream down to a whisper. That's what makes it a great player. It's that fully responsive connection between what the mind conceives and what the machine delivers. I change dynamics to musically shape every note I play. Dynamics are the main expressive quality in the concertina. A narrow dynamic range in an instrument feels very dead and restrictive, not much fun to play. Please, in your work, emulate the best instruments and player abilities.

 

I would like to hear some kind of adjustable logarithmic algorithm that makes the bellows more or less sensitive to change at the quietest end of the dynamic spectrum... or perhaps to have several parameters of adjustments to control how sensitive a player wants to be at varying levels of loudness. That could be midi heaven.

 

Midi volume runs from 0 to 127. I want to be able to play expressively in the 0 to 50 range with only occasional outbursts above. That would give me the headroom needed for expressive playing and more closely approximate a real acoustic instrument that can growl and speak like a living voice.

 

--------

 

Then there is the related issue of articulation.

 

If I load the bellows with pressure (in or out) and then depress a button it makes one kind of sound envelope. On the other hand, if I depress the button with no bellows pressure there is no sound. Keeping the button depressed and adding pressure makes the note sound with a different envelope depending on the pressure applied. This ability to choose which of these two articulation models is used is also key to musical sounding playing on the squeezebox and a realistic midi instrument.

 

The attack is quite audibly different between these two articulations and a midi controller would ideally be sensitive enough to realize these differences in the sounds. It's all just bellows pressure data plus note on and off commands. Really should not be a problem.

 

The reason why this is important is that all concertinas are very limited in their ability to vary the normal expressive qualities of timbre or pitch of a note... just compare their ability to that of string or wind instruments which can play around with this at will. The only expressive quality for the poor limited squeezebox is expressed in relative volume sensibilities and at that, the concertina can excel and find it's voice... if you make your midi with the capacity to play that way.


Edited by Jody Kruskal, 26 April 2016 - 02:52 AM.


#46 JimMacArthur

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Posted 26 April 2016 - 07:43 AM

Jody, yes, yes, yes, I couldn't agree more.  For me, the holy grail of this work is a better sounding, more responsive instrument -- one whose virtual reeds start to sound --reliably -- at the slightest pressure.  I suspect that the long path will use a technique called modeling synthesis, but I'm starting to see some success with simple sample players.  The trick is to record lots of samples -- at least one for every note -- with various amounts of bellows loading.  If you only record one sample per note, it should should be with the bellows moderately loaded before the attack.  Then the synthesis algorithm is straightforward: the synthesizer plays the sample when the button is pressed, and modulates it with (suitably remapped and filtered) pressure information.  If the bellows has pressure when the button is pressed, the result is a loaded attack.  If not, the result is a crescendo into the sustain part of the sample.  It's simple, and it won't fool a discerning listener, but you can use the technique to make an instrument with far more dynamic range than an acoustic concertina.  And you're right -- there's nothing in the MIDI protocol that restricts what we want -- the onus is on the synthesizer designers.

 

Robert, I happen to work in one of the confluences of human knowledge (Harvard University), and have access to several experts on elastomeric foam, some of whom owe me favors.  One of them will look for polyurethane foams which most closely approximate springs, although he expressed some doubt.  Another wants to go another route -- he's looking into foams which change their electrical properties (conductivity, permittivity, permeability) with pressure.  These already exist, but they're far too dense to have the right feel.  If he finds something, we could combine the spring and the position sensing into one simple, low-cost design.

 

Re circuit boards costs, you will find that board costs have dropped dramatically over the past few years, with the emergence of "pooling" services that combine several designs into one run.  I regularly get a few pieces of a simple design for less than $20 a piece.  In fact, the prices are so low that I now find it cheaper to have a board made than to blow an hour drilling holes into panels. That's why the end plates of my concertinas start out as $15 circuit boards before I dress them up.  It might well be cheaper to swap our designs by email and have them made locally than to deal with customs.



#47 conzertino

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Posted 26 April 2016 - 11:27 AM

It worked! My remark about dynamics for anglos was provocative! On the other hand, from my experience it is really difficult to come up a satisfactury dynamic control! We had some discussions on the topic in another thread. One problem is that every instrument has a different dynamic behaviour. And as I like to play a variety of instruments on my midi, the programming gets tough!

 

The other reason for my remark was that it would be nice to have a really inexpensive concertina on the market - the sort of thing you could give to a child for christmas...  And just like some of the cheap keyboards around don't have dynamic control, a beginner's box could live without. Dynamic could then be added at extra cost at a later stage...  

 

Just look at the price of the midi-concertinas on the market!

 

With regards to the printed circuit-boards: as the cost of the elctronics devices has dropped dramatically ( all components on my anglo ( see above ) cost less than 10$! ), but large PCBs with through-hole-plating and drilled are still quite costly in small quantities!?

 

Unfortunately I'm very busy this summer. I would love to be part of a development-team, but I can't do the whole job!

 

The first major question is, which system to build first!?! There are loads of anglo players around and there is a definite shortage of Haydens, but I would start wich a small 40 key English-system!?

 

The next step should be to find an anglo-maker for the swap pans-version...



#48 Don Taylor

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Posted 26 April 2016 - 01:15 PM

Jody:

 

Thanks for the input and especially for pointing out the need for articulation as well as simple dynamics.

 

I could go one step further and mention the sort of acrobatic dynamics that some folks achieve (Alistair Anderson for example) by waving their concertinas around in the air.

 

Robert:

 

Re: BLE (Bluetooth Low Energy) latency:  Please correct me if I am wrong, but I think that you use Bluetooth to transmit midi commands to your iPad and not the final audio?  The final audio connection being a physical wire to an amplifier + speaker? 

 

I ask because it is my understanding that audio via Bluetooth does introduce noticeable latency and I think that Jim is proposing to build an on board synthesizer and, presumably, ship the final audio out via Bluetooth.

 

 

Don.



#49 conzertino

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Posted 26 April 2016 - 01:46 PM

Don, you are right. As I pointed out in my video, the latency between my BLE transmitter and the I-pod is negligible, the latency from the Ipod to the BLE amp is about 1/2 second!!

 

I think that Jim just wants to plug in his ear-phones - or an amp by cable!?



#50 JimMacArthur

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Posted 26 April 2016 - 02:11 PM

Yup.  Several sources give the BLE midi spec at 6 msec.  Bluetooth audio latency varies with the driver, but is usually over 100msec.  I've got a headphone amp in my concertina, so I'm all self-contained, and if I want a wireless link, it will be transmitting MIDI data, not audio.



#51 Don Taylor

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Posted 27 April 2016 - 01:55 PM

Robert

What kind of usable range (distance) are you getting with your analog Hall sensor in a piston?

Thx. Don.

 

Added later:  I have found examples where folks can measure up to about 15 mm depending upon the strength of the magnet


Edited by Don Taylor, 28 April 2016 - 11:21 AM.


#52 Steve Wilson

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Posted 03 May 2016 - 06:47 PM

I take my hat off to all involved in the development of midi concertinas.  Great work is being done by the likes of Bruce, Robert and Jim and others I'm sure. I encourage you all to pursue this midi project with urgency cause I want one for Christmas.

 

What Alex Wade has been doing with primary school children is exciting. 

Concertina In Public Education

Started by Noel Ways, 24 Apr 2016  

 

Cheap concertinas and motivated teachers could advance concertina usage significantly



#53 eskin

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Posted 05 May 2016 - 12:50 AM

If you need per note concertina samples, I have them available for use in the project, they are same ones I recorded for my iOS apps.

#54 JimMacArthur

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Posted 05 May 2016 - 07:18 AM

That's very generous, Michael, but we'll need to make sure we protect your IP.  In my box especially, those samples would be hanging out in soundfont files on a microSD card.  Come to think of it, though, we could probably think of ways to encrypt the files well enough to discourage casual theft.






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