Bass Pedalboard chip

[R.G.]

One of my long-term quests is generating musical notes from a programmable microprocessor. No, don't ask why. Just because.

I came up with a design recently that's suitable (I think) for making a bass-note pedalboard. Press a foot-key, get a bass note.

Code's in test, and not fully working yet, but someday, it will be.

So I wanted to ask - any ideas about a good or easy to find/make (a) foot or (b) mount-on-the-guitar mini-hand keyboard. Any good ideas?

[olddawg]

Why not use a midi interface like everyone else?

[Enzo]

I THINK he is asking for help designing the keybed itself - the buttons you push.


If it is a one-off, you might just find a dumpster home organ with a foot pedal assembly and steal it. SOme of those had a one octave pedal set.

[Mick Bailey]

I take it you only need to generate a single output per key and the code will deal with the rest (trigger/gate or whatever the digital equivalent would be). I've used PCB tactile switches as they are, soldered to a DIY PCB and mounted in a slim plastc case. With careful marking and cutting the holes can be cut to leave the switch body flush and the pads slightly raised. Just velcro to the scratchplate. It has a 'button accordion' look but works fine. You have the benefit of being able to curve the keyboard to fit a particular guitar and RH ergonomics.

Now, a nice thing with a processor is that you can arrange 5 buttons in a 'thumb+4 finger' hand shape and get far more than an octave out of button combinations - rather like the 'Microwriter' keyboard concept.

Take a look on MFOS for construction ideas for keyboards/pedals. Ceramic magnets and reed switches are popular. Traditional bass pedal setups (or the Moog Taurus) are a bulky thing which could usefully do with reducing in size. I like the idea of a guitar mounted setup.

[R.G.]

Why not use a midi interface like everyone else?

MIDI is the work of the Devil, and incomprenhensible even to a professional EE/progammer with experience.

Well, OK, it's overly complicated for a 14-pin single-chip tone generator.

If it is a one-off, you might just find a dumpster home organ with a foot pedal assembly and steal it. SOme of those had a one octave pedal set.

Did that. I have a footpedal setup from a home organ. The chip design is actually chainable to add octaves. I will use that for my own setup.

Part of the (implied) question is whether other people are interested and motivated enough to think of how they'd set it up. One of my ideas was for a guitar mounted rig. I forgot to mention that by flipping a switch the chip will also go to on-off mode on the keys, and generate a drone-tone. I like bagpipes too. No, not because of the men wearing skirts. Just because.

I should have added to this that this is not a commercial venture. I just can't not design. Can't turn it off.

I take it you only need to generate a single output per key and the code will deal with the rest (trigger/gate or whatever the digital equivalent would be).

That's correct. The chip plus some resistors actually generates a sawtooth wave, which is a reasonable first step toward a string tone. The note turns on and off from the key input inside the chip - press a key, note on; release, note off. Or, if the drone jumper is on, press a key, note on. Press again, note off.

I've used PCB tactile switches as they are, soldered to a DIY PCB and mounted in a slim plastc case. With careful marking and cutting the holes can be cut to leave the switch body flush and the pads slightly raised. Just velcro to the scratchplate. It has a 'button accordion' look but works fine. You have the benefit of being able to curve the keyboard to fit a particular guitar and RH ergonomics.

Now, a nice thing with a processor is that you can arrange 5 buttons in a 'thumb+4 finger' hand shape and get far more than an octave out of button combinations - rather like the 'Microwriter' keyboard concept.

Take a look on MFOS for construction ideas for keyboards/pedals. Ceramic magnets and reed switches are popular. Traditional bass pedal setups (or the Moog Taurus) are a bulky thing which could usefully do with reducing in size. I like the idea of a guitar mounted setup.

Mmmmm. Good idea. Best I had come up with was using twelve tactiles arranged in a crude imitation of a piano/organ keyboard.

Hmmm. I wonder what the "active rug" things do - the game setups where you step on one or more areas of a rolled-out "active rug" and the machine senses it.

[Mark Hammer]

Is there any way the Source Audio Hot Hand 3 might be of service? It outputs two 0-3.3v control voltages, corresponding to two dimensions of hand movement, and a 0-10k resistace change for the third dimension.

Or is the bass note stream you imagine more complex than what swinging one's hand around between strums might generate?

[R.G.]

You know, I started to respond with "no, that won't work - this thing uses switches..." and about there I stopped and realized that what it actually does is read an input voltage and by software cut that into bins of between x and y, y and z, z and a... and so on for an octave.

Fed an analog voltage, it would step neatly between discrete notes when the analog voltage read went over/under into a different range of voltage. It's hooked to 0-5V now, but perhaps that could be tinkered to 0-3.3.

Mark, you gotta quit doing this to me. This thing is about 44% bells and 42% whistles now, only about 4% real stuff underneath all that.

[Mark Hammer]

Harry Bissell came over to my place a decade back, and brought a theremin-with-quantizer with him. It allowed for hand movements to produce a keyboard-like effect. Granted, it was a bit like playing the piano with your rolled-up fist on the black keys, but it worked, and you got real notes out of it, instead of unpredictable sci-fi sounds. With practice you could get random access to specific notes.

I think there's a lot more potential in the Hot Hand than people give it credit for. I'm hoping to score me one soon. The guys over at Source Audio were eager to provide info that would potentially let me apply the unit in unplanned ways. I see no reason why they would not be as helpful to you too.

And...sorry.

[Mick Bailey]

I initially rigged up an extremely primitive 1 octave 1V/oct keyboard to see how I'd like controlling my modular synth from the guitar. It was just strips of PCB to represent keys. A solder bumb was the contact and it worked (and still does work) reliably after 5 years. One thing you won't be getting with digital is S&H droop on a long note. Tactile keys work very reliably and are cheap so I moved on to those. I didn't take the idea further because I got distracted into experimenting with stop/step sequencing. A single switch increments a sequencer to the next step. The idea was to pre-program the note changes and then a press of the momentary switch flipped to the next note. This was analogue - digital would be much better as the patterns could be saved in banks and key-related arpeggios generated.

Just thinking for a bass synth you'll need ADSR control as well as filtering - I see a lot of coding there.....

[R.G.]

I think I'd save the ADSR for a second chip.

Mmmm... good idea there, though. I have another unused pin. I could have a "note is on" output. This would directly key an ADS(R) circuit, with some reservations.

R is in quotations because I can't see any direct way to make it possible inside a single small chip. When the key is up, output is off. But ADS is easily possible with an external circuit, perhaps something really trivial. I like the orthogonality of a separate ADSR chip. Hmmm. OK, just designed it in my head. Another 14 pin uC, which reads the "note on" state, and pulls down resistors through the LED of an LED/LDR module for controlling loudness. Or current into an OTA. Several ways.

But it keeps the note function in a single chip, which is where I started this.

I'm looking at the single chip as doing:

- one set of notes from top octave to lowest octave for an organ generator
- guitar tuner
- guitar bass accompaniment/footpedal
- guitar background drone-tone

All of those are trivia attached on top of the note generation, and all are actually inside the existing chip code except the tuner.

[Mick Bailey]

Just another chip...just one more... got me to here;