key thumper

for sampling my rhodes

I’m planning to sample my rhodes. I’m probably going to buy a copy of Scarbee Rhodes, which so far seems the best, but it’s missing something I want that my trusty old rhodes still has.

Anyone have any good ideas on how to build a key thumper?

I was thinking of using a solenoid, but a friend who should know says that they’re not very precise, and gravity makes a better (more reliable/repeatable) driving force.

Yeah, I know it’s a lot of work and probably won’t end up as nice as available cheap or free ones. But I haven’t dismissed the idea yet. I might also sample my acoustic guitar, BTW. I’ve done samples before and been happy with the results. The tools are WAY better & easier to use now, but the bar is higher too!

Hi Jeff:
You’ve taken on a fastenating project… There’s a lot of guys that would like to have those samples in their collection… You might think about looking into finding the Rhodes Maintenance manual to do a Tyne-to-Pick-up adjustment before you get into the sampleing part of your project. There’s a relation between the positioning of the Tyne to the pickup so that the tonal harmonics are even over the keyboard, from top-to-bottom-end… Just makeing a suggestion…

Another keyboard that would be interesting to sample is, a Wurlitizer A-77 Keyboard… I am beginning to hear commerical songs that use them … Ya can’t get a synth to repro that sound… Well…


Just to clarify, because I find the idea interesting, not because I have anything useful to say - you want a mechanism that can be set to hit the keys at precise velocities, so you can get a multi sample of each key at consistently varying velocities, right? How is this normally done? ???

Someone on another forum mentioned that Kurzweil used a “thumper”, and I like the term. :) I have no idea what other folks do, but I may send some email to folks who’ve sampled Rhodes.

What I expect to do is set up the gizmo for one velocity and sample each white key (sliding it along rails clamped to the keyboard), then set it up for a higher velocity and sample each key again, etc. At least three times, and 4 or 5 would be a lot better. If I were fussy, I’d also sample release and pedal-down as well as pedal-up. But I don’t think that’s necessary for my purposes. I want realism, but not down to the warts and peach fuzz.

If someone will loan me a Wurly, I’ll be happy to sample it! I haven’t found a decent Wurly soundfont yet, even though I think it’s easier than Rhodes. To my ear, a Wurly doesn’t change timbre as much with velocity. I’ve heard decent synth Wurly sounds, but my current synth’s Wurly is horrible.

Thinking, thinking…a home mechanism to do this… Suppose you have a little hammer (with something to evolve it to make it soft) with an arm (maybe made with a Microphone stand) You put it always at the same distance of the keyboard, you release it to hit the key. To have diffrent velocitys, you can add objects of diffrent weights to the hammer.
mmm… describe my idea in english, you understand anything?:p

I have a wurli.

I had the chance to become the owner of one, and I tossed the idea away… It was the right price, as I thought, as well…

It’s sensitive to touch to a small degree… But not as much as say a Rhodes, or an acoustic piano…

Who was the '70’s group that made the Wurlitizer piano popular? Were they called Supertramp? Or something like that?? What was the name of the song? The winner gets a free plug-in… :laugh:


Marce, you’ve got the right idea, but I don’t think I’m going to hack it quite that bad. I’m thinking of something that slides along rails that are clamped to the keyboard. I do plan to use a hinge and an arcing motion, because a hinge is easier than a slip bearing. But the hardware will be to one side of the key being pressed, sitting on the rails. When I get towards the other end, I’ll just reverse the apparatus.

The hard part will be getting repeatable results for the lightest keystrokes, but those are very important for the sound I want. (So are the really hard ones …)

Jeff, what a fascinating project!

I was going to suggest, (being incredibly ignorant about keyboards), that you ignore the keys, and just get inside those electronics.

However, having looked at the manual


I see that it works nothing like I imagined it. (I sort of thought that velocity was determined by the time it took the key to travel between one bus and another. What a dumbbell! LOL)

So, I can see you have three ways of activating your thumper.


A well built and well maintained solenoid can be consistent, but not as much as the other two.

Springs are more consistent; their effect does alter as they age, but not probably during the time of your sampling.

Gravity is very consistent (during my lifetime anyway :) ),

So I think just a simple “dropping” of a weight seems to be the best option.

But, how to do it? Buggered if I know! :D (but I’m thinking about it :) ).


Gravity, hmm? A small tube witha metal pipe to act as the hammer in it, with something to hold it in the tube at various heights, e.g., a quick release of some sort? Shouldn’t be too hard to make out of stuff from the hardware store, should it? Then calculate the force from 1 cm, 1.5 cm, 2 cm, etc. Even if your calculations are just approximate, you could use them as a starting point and just listen to the results to figure out what heights will get what you need. You wouldn’t really need to test the force directly.

A tube Tom, that sounds a very simple but very practical idea.

But, instead of holding the tube at various heights, you could have the bottom of the tube resting on the key, and vary the length of the tube.

My granddaughter has a toy with which she can fit small lengths of 2.5 cm diameter plastic tube together to make longer and longer tubes.

Then it’s just a case of dropping a padded steel ball or piston down it I suppose.

However, that doesn’t necessarily mean that a consistent amount of force is applied. But, a consistent amount of energy is.

But, whether that uniform energy is converted into a uniform force, and hence uniform velocity, depends on the inertia and resistance of every key being the same.


Right, seems to me that when I’m playing the wurli I have to compensate (a lot as it turns out) for the variable levels the same velocities give on different keys… so record stuff and then listen and adjust as needed.

Just different lenghts of tube, and a padded ball - that is soooo simple. :)

I think you’ve got it Tom; quick, patent it! :D

Just a few more thoughts: Perhaps a cylinder would be better, that way you can put a blob of putty or something on the end to stop it bouncing.

And of course, the weight of the cylinder would have to be enough to keep the key depressed.


I think air resistance will get in the way with the tube, unless the tube is made of screen. In any case, I think it will work better with an arc motion, since good hinges are easy to find. A standard door hinge on a 2x4 should work just fine.

I think a hinge-based mechanism sounds reasonable enough. My feeble imagination tells me the biggest challenge will be getting a very light stroke without any bouncing. Human hands can lightly touch the keys while adding constant pressure afterward to keep the keys down. Perhaps a heavier weight at point-blank could work since it won’t have time to accelerate much?

Also, are you doing direct-in recording, or are you going to mic an amp? If it’s the latter, I suppose silent operation will be critical. Anyway, it sounds like some serious trial-and-error to me…but it sounds kinda fun. And I’m sure you’ll say it was worth every minute after you have the finished product!


Well, I got a copy of Scarbee Rhodes cheap on ebay, so this project becomes less important. But I STILL think I might give it a go. Been fooling around with 2x4s & what-not today, trying a couple things. Bounce isn’t a problem. Just as we figured, the lightest strikes are the hardest ones to do repeatably.

what am I missing? Why not play the notes on the keyboard at different velocities and record the sound?? Any subtle differences in volume could be corrected in a digital editor.

It isn’t just the volume that changes. With a rhodes, the tone changes dramatically with velocity. If I don’t get fairly consistent velocities when I sample, the tone will change from key to key. And it wouldn’t be subtle.

Of course, as someone already mentioned, the action isn’t perfect so there will be some key-to-key variation anyway. But I want to minimize that, and I can always resample any keys that stick out too much.

If I was a great technical keyboardist, perhaps I could just play the notes steadily. But I find I can only get consistent dynamics when playing music or scales, not when playing a single note.

Quote (learjeff @ Oct. 07 2004,17:40)
I think air resistance will get in the way with the tube, unless the tube is made of screen. In any case, I think it will work better with an arc motion, since good hinges are easy to find. A standard door hinge on a 2x4 should work just fine.

Good point. If the ball were enough smaller than the tube, the air resistence wouldn't matter, it'd just be one of the variables that determine the velocity. But I like the hinge idea.

Hey, Ali, didn't someone already patent the idea of a ball movnig throught he tube with some velocity? Smith or Colt or someone like that. :)