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I'm wondering what challenges there would be in making your own MIDI controller out of an old grand piano action? What do you think? I imagine that as just taking the entire action out and mounting it in an enclosure where the hammers would rebound from some surface instead of strings. Then the questions is how to detect hammer velocity, e.g. how easy it is to make optical velocity sensors at each hammer. Then you'd need also key sensors so that you can send note-off messages. In a first iteration that would just be a simple on-off sensor since in MIDI this isn't a continuous control if I am not mistaken? And then there's the controller part that will translate that to MIDI. Not sure if something like a Raspberry is quick enough to be able to do that but I guess so.

Have you considered such a solution, its feasibility and whether it would ultimately be cheaper than the current cheapest hybrid piano such as the N1? I believe one can find pretty cheap grand pianos that are broken but whose actions are still relatively preserved so the most expensive part of such a solution might be had for how much? 500-1000?

Last edited by CyberGene; 02/13/18 08:55 AM.

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VERY hard to do, due to the needed precision and calibration.
I don't think it is possible to DIY it "just like that". You would need to be a pro in both fields fields: E-tech/IT tech in order to handle sensor hardware + programming and piano tech in order to handle piano parts.

I also don't think that you would end up cheaper, at least not if you calculate the hundreds of man hours you would need to dump into such a project fairly.


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Don't they sell this as a turnkey retrofit for any piano? Silent piano/PianoDisc?

I think the midi stop is key sensors only (so closer to the NU1 mechanism than the N1/2/3 but I'd say almost all the work is already done, so no point reinventing the wheel?


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Originally Posted by Gombessa
Don't they sell this as a turnkey retrofit for any piano? Silent piano/PianoDisc?


I think those use only key sensors and I think we would all agree hammer sensors are the only way.


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Unless the project itself is the motivation (the journey is the reward) if you consider the money and man hours you would need to spend, it would be much cheaper and quicker to put a fraction of those man hours into a second job (flipping burgers or something) to earn the money to buy an N1 or comparable.


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Here's another option - just but an old grand with a factory silent option built in. The Kawai anytime x2 has hammer sensors, as does the Yamaha SH.

If you really want to DIY it, take the sensors and shutters off and transplant it to the action of your choice (probably still a huge amount of work, but 90% of the job is done already).


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Creating something with your hands is always rewarding. I'm not the best example since the only thing I've created recently is a hybrid headphone amplifier with the Korg NuTube and it was rather easy since I used a ready PCB and schematics so I soldered it in two hours. But the experience was absolutely rewarding! I listen through this amp all the time at the office:
[Linked Image]

The sound is very warm because the tube is a modern one created by Korg for guitar effects with exactly the purpose of accentuating the even harmonics which are mostly consonant intervals smile

Anyway, money is also a consideration. I would personally undertake a DIY controller project both for fun and to save money provided it's at least half the money of a N1.

BTW, where I live, one should flip burgers his whole life to purchase a N1, provided he eats own food for free and sleeps at the "office" laugh


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The Moog Piano Bar lets you generate MIDI from a physical piano action. They don't make it any more, but you might be able to come across a used one. I seem to remember that some other company has something similar, too.

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Originally Posted by CyberGene
I think we would all agree hammer sensors are the only way.

Why is that? Isn't the hammer movement a function of the key movement, so any data that can be gathered from the hammer can also be gained from the key? And the greatest piano touch and technique comes not from playing hammers, but playing keys.


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Originally Posted by toddy
Originally Posted by CyberGene
I think we would all agree hammer sensors are the only way.

Why is that? Isn't the hammer movement a function of the key movement, so any data that can be gathered from the hammer can also be gained from the key? And the greatest piano touch and technique comes not from playing hammers, but playing keys.


I can answer with a real world example: the NU1(X) loud note problem. It's because there are only key sensors and no hammer sensors. Since this is a real upright action, you can be in the situation where the hammer is detached from the key (jammed, locked... not sure about the correct term) and the key suddenly becomes lighter and you can easily press it with high velocity. On a real piano that would result in no sound. On NU1 that results in sudden loud velocity because the key sensor is not aware of the hammer situation and thinks you're just banging it loudly which isn't the case. I believe some very precise, clever and powerful calculation would be able to actually predict when that would be happening by just modeling how the hammer would've behaved in every possible situation but apparently that's not the case with NU1 hence it might not be possible to do that. So it might be beneficial to just implement optical sensors at the hammers which is what the more expensive N-series and now Novus employ and there's certainly a reason why they use both key and hammer sensors, not just key sensors.


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Originally Posted by Gombessa
Here's another option - just but an old grand with a factory silent option built in. The Kawai anytime x2 has hammer sensors, as does the Yamaha SH.

If you really want to DIY it, take the sensors and shutters off and transplant it to the action of your choice (probably still a huge amount of work, but 90% of the job is done already).


Well if you're buying a second hand grand the action presumably comes with it?

You'd either just transplant action and digital parts to a new smaller cabinet and add a speaker system. Or retrofit the piano (assuming it's not already a transacoustic or an ATX2-f variant) with a soundboard transducer and speakers.

Also you get a whole acoustic grand with a second hand piano. laugh Obviously the acoustic parts might also need refurbishment but if someone is DIY competent enough for the rest of such a project then I doubt reasonble restoration of the acoustic elements is out of their ability either. Most of it is not, as the saying goes, rocket science, it's just quite a bit of work and needs an appropriate amount of care and attention.

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Unless you have some serious precision machinery, I doubt a decent, usable DIY grand action controller based on optical sensors is viable. Even slightly mispositioning optical sensors can lead to dramatically different behaviour. The most common problem we have on our MRI machine is actually caused by an optical sensor moving out of place due to vibrations.

That said, it would be a very interesting project.


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Originally Posted by CyberGene
Originally Posted by toddy
Originally Posted by CyberGene
I think we would all agree hammer sensors are the only way.

Why is that? Isn't the hammer movement a function of the key movement, so any data that can be gathered from the hammer can also be gained from the key? And the greatest piano touch and technique comes not from playing hammers, but playing keys.


I can answer with a real world example: the NU1(X) loud note problem. It's because there are only key sensors and no hammer sensors. Since this is a real upright action, you can be in the situation where the hammer is detached from the key (jammed, locked... not sure about the correct term) and the key suddenly becomes lighter and you can easily press it with high velocity. On a real piano that would result in no sound. On NU1 that results in sudden loud velocity because the key sensor is not aware of the hammer situation and thinks you're just banging it loudly which isn't the case. I believe some very precise, clever and powerful calculation would be able to actually predict when that would be happening by just modeling how the hammer would've behaved in every possible situation but apparently that's not the case with NU1 hence it might not be possible to do that. So it might be beneficial to just implement optical sensors at the hammers which is what the more expensive N-series and now Novus employ and there's certainly a reason why they use both key and hammer sensors, not just key sensors.

Right, I see what you mean. That's an unfortunate artifact of a certain hybrid set up, if I understood you correctly. This doesn't happen on the 'standard' DP hammer actions, presumably because the hammer doesn't have a free flying phase, and key & hammer always remain linked to each other.


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I wouldn't say that getting any old action will do for this application. If you wanted to use hammer sensors you would need an action that is in excellent condition so that there is no lost motion, and also for good repetition. Most old actions need some work - some need a lot of work. I wouldn't necessarily say that getting an action out of a donor piano is going to be cheap. You could sink quite a bit of money and/or time into getting it regulated, changing felts, and possibly redoing the centre pins and bushes. There is also the keyboard - which will need to come from the same piano. What condition will that be in? Will it need front rail pin bushes redone? Balance rail bushes? In fact, the only thing that isn't relevant to the performance of this action is the hammers.

So I think this project could cost a great deal more than you might think if it's going to perform well. It's easy to overlook that because Yamaha and Kawai use new actions in their hybrids and the consequences of worn action components hasn't been generally felt yet - given the relatively young age of most hybrids. I remember Dave Horne mentioning his Grand Touch and AG have had some regulation work done on them - presumably because they weren't feeling right anymore. They were brand new actions, so when I think of an old action, I think of a range of issues that require a lot of time, knowledge and money.

This is before you even start with the sensors, etc. I see this project being a money pit that makes the N1, NV10 look rather cheap!

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ando, you bring some really strong points, thank you for this answer!


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A huge & cool DIY project. I've been noodling on this for a while. Even with some "commercial" systems, calibration and/or muting can be challenging.

Pianoteq forums were illuminating (a few expereinced guys and piano tuners had difficulty calibrating commercial systems and some just gave up):

http://www.forum-pianoteq.com/viewtopic.php?id=760
https://www.forum-pianoteq.com/viewtopic.php?id=3584

DIY systems in action or in-process (basic schematics and shows level of complexity):

http://www.instructables.com/id/Adding-MIDI-to-Old-Home-Organs/
https://groupdiy.com/index.php?topic=62509.0
https://www.youtube.com/watch?v=fUHbq3j0ObE
https://www.youtube.com/watch?v=Asjjw7bALeI

These interesting commercial "articles" will get you started (the first has a ton of photos):

http://forum.pianoworld.com/ubbthre...of-pnoscan-ii-stop-rail.html#Post2533658

https://www.pianobuyer.com/Articles/Detail/ArticleId/42/HYBRID-PIANOS

For more inspiration, I would start the search with commercial system terms in Bing (or whatever) then go from there. Also, there are some helpful posts pre-2014 (pianoworld only allows one to search 4 year periods so you need to adjust the search engine to get older results).

http://www.qrsmusic.com/PNOScan.asp
http://www.prorecord.info/
http://www.pianodisc.com/quiettime-magic-star/

This is a neat DIY project but might be much cheaper and easier to go commercial. The devil is in the details and getting rapid response consistently all the time will be the biggest challenge in my view. Getting sloppy results will be "easier" but unplayable:

- For DIY, you need to buy, install, wire, calibrate a lot of parts which will cost a few hundred Euro and take a lot of time.

- And you need to figure how to get all key and pedal information into a MIDI signal in about 1ms with little variance and zero glitches. Arduino is cheapest and easiest but not really designed for this level of processing so customizing speedy hardware & software will take some effort.

- I would want to engineer some high resolution MIDI scheme for fun (maybe only works on PianoTeq today and not convinced you will notice a difference).

- You need to borrow a decent oscilloscope for troubleshooting and good calibration.

I can imagine many ways how Yamaha, Kawai etal. might run "instant" automated calibration schemes with a push of a button @ the factory for their "premium digital pianos"; that could address variability in assembly and sensors.

Good luck!

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newer_player, wow, thanks, a lot of great information!

Right now this all seems like a way too difficult task. But I could eventually try it some day, entirely out of geekiness, with the clear mind it won't probably produce anything usable at the end smile


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Getting a DIY system to the level of a commercial system would take some effort.

And the two PianoTeq forum posts indicate how difficult it is to harmonize the physical regulation and MIDI velocity curve with commercial systems. Well worth a quick read!

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Originally Posted by toddy
Originally Posted by CyberGene

I can answer with a real world example: the NU1(X) loud note problem. It's because there are only key sensors and no hammer sensors. Since this is a real upright action, you can be in the situation where the hammer is detached from the key (jammed, locked... not sure about the correct term) and the key suddenly becomes lighter and you can easily press it with high velocity.

Right, I see what you mean. That's an unfortunate artifact of a certain hybrid set up, if I understood you correctly. This doesn't happen on the 'standard' DP hammer actions, presumably because the hammer doesn't have a free flying phase, and key & hammer always remain linked to each other.


Is that actually the cause behind the loud note problem? that explanation has always struck me as a little unlikely. My impression is that the loud note was a maximum velocity one, not just a bit louder. It seems unlikely that someone would suddenly go straight to max velocity just because the hammer was no longer engaged.

Regardless, relying on key sensors only for an acoustic really isn't going to provide a great sense of connection and the physics required to constantly calculate the hammer position would likely be more complicated than simply adding hammer sensors. Kawai have managed to fit optical hammer sensors on their silent uprights, I think yamaha are just sitting on their laurels a bit here.

On most DPs the hammer can detach but the way the mass is split between the two parts (opposed to the three 'parts' of an acoustic) means it is fairly rare. That said, most DPs despite that still have the sensors triggered by the hammer.

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I actually built such a thing many years ago (like over 25). Back when weighted 88 key controllers were expensive. It was a fun project, and quite an experience. It worked quite well to, although wouldn't have the finesse of modern day keyboards. I used an old upright piano keyboard, with steel weights on the end of the keys. The processor was an old XT motherboard (I told you this goes back a while...) to which I added a serial card for MIDI output (changed the crystal from 14.74 kHz to 16 khz to get the MIDI baud rate and modified for current loop operation), plus a breadboard style full length ISA card on which I designed the interface to the keyboard, controls and display. The ISA card mostly had a bunch of 8255 I/O chips, on which I used 2 bits per note. It also had a free running 16 bit counter that I could read on the fly. The keys each had 2 contacts (platinum plated wires obtained from an old organ keyboard). With the key at rest, one contact would touch a bus bar connected to common. Pressing the key would cause that contact to open. When the key was near the bottom of its travel, the second contact would touch another bus bar, also connected to common. Each key was thus either at rest, in movement (no contacts touching) or at the bottom.

It worked like this: the program (written in DOS assembler) would read groups of 8 notes, looking for any key that was no longer at rest. If that was the case then a status byte for that key was updated to reflect that it was in movement, and I'd read the 16 bit counter as a kind of time stamp and store that as a starting counter value. Each key had its own status byte and counter value memory location. On subsequent scans any key that had a status of being in movement was tested for bottoming out. If so, then the status was again updated and the counter read again. Using subtraction I was able to get a velocity value for that key by comparing the new value against the starting counter value (accounting for possible counter rollover) I'd then look that up in a velocity curve table (I had created several) and got a corresponding MIDI velocity value. I would then output the Note ON, Note number, and velocity bytes out of the serial port. Finally, from the bottomed out status, I'd look for the "at rest" contact being detected again on subsequent passes, to send out the needed MIDI Note Off event. There was also a sustain pedal, needing a single input bit.

I had velocity curves, splits, transposition and programmable buttons (to send out things like MIDI Program Changes), controlled by 24 buttons and a 16 character LCD readout. Building it was fun, and the learning experience was worth even more. I might not have the IT job that I have now without doing these crazy projects!


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