Wednesday, 29 January 2014

One Evening Project

Easy MIDI Bass Pedals

from your old MIDI keyboard                             

Moog Taurus. Image source Wikimedia Commons.

Organ pedalboards have existed since 13th century. The idea is fantastic! You can use your feet for bass duties while your fingers are busy playing higher registers. Of course you can also use MIDI pedalboards for playing higher sounds or triggering samples and fx or whatever you like.

I was interested to try using bass pedals while playing my electric guitar.
Many rock groups such as The Police and Rush have used bass pedals (in power trio context). 
They used the legendary Moog Taurus - the most famous foot-operated synthesizer.

Taurus 3 is a dream machine but it's like 2000 dollars! And it has only one octave keyboard.

MIDI bass pedals like 12 step by Keith McMillen is more reasonably priced and comes with cool smart sensor keys. It's also has only one octave of keys.

But what if you wan't to try the idea of bass pedals first before buying expensive product.
Maybe you already own something like 12 step but need second machine for triggering samples.

Do you have an old ROMpler keyboard collecting dust? Give a new life to your Casio home keyboard!
You will need a working normal size keyboard (at least 4 octaves) that can output MIDI messages.
I'll show you how to hack it to MIDI bass pedals machine nondestructively!
Yes! Nondestructively. You can reverse this hack if you want to. 

Maybe I'll buy something like 12 step one day but for now I'm perfectly happy with my home made bass pedals hack. I can create cinematic atmospheres with my guitar and play droning bass notes at the same time with my feet like a musical octopus! It's super cool to play some guitar arpeggios with delay fx and try different bass notes - A Happy Accident Generator Extraordinaire!

I hacked my Yamaha SY-35 vector synthesizer. It's a cool synth but not used so often nowadays.  
The other two MIDI capable keyboards I own are E-mu Emax and Roland PC-180A midi controller so SY-35 was the best option. 

Yamaha SY-35 hacked to bass pedals. Yamaha's modulation wheel is also usable as a foot-wheel.

What You Need

Normal size keyboard instrument (at least 49 keys preferably 61 keys) with MIDI output capability

Double sided tape

Normal clear tape

Masking tape

Thin black and white plastic sheets

I like to use polystyrene sheets in my projects

You can also use something like

It should be something thin but quite sturdy material

 I used these cheap containers as a white plastic source

Coloured cardboard (some color other than black or white)

Cutting tools

Marker pen and a ruler


Computer with DAW / VST host / Pure Data / Program that manipulates MIDI messages

Making of Bass Pedals


Clean your poor keyboard from dust and hair. :)

Cut white key sized pieces from coloured cardboard and attach them to following locations with double sided tape. These will work as spacers.

double sided tape 

Spacers in place. You don't have to cover the whole surface of the white key with coloured cardboard.

Make spacers more sturdier by covering them with clear tape

 Clear tape on top of areas where your feet might touch


Use again double sided tape for attachment. Cut white and black plastic to pieces you see in the next picture. You can cut thin plastic with large scissors. 

Attach a piece of coloured cardboard on top of C#3 and D#3 note.

Then make these white plastic pieces and fix them in top of white keys.

If you have 49 key keyboard just ignore the last octave of the instructions. You still get more than an octave of bass pedal keys. 

Now mark the keys with marker pen. Use masking tape on black plastic. 

I made E the lowest note. I didn't want to go as low as C1. It's 32.7 Hz.
E1 is 41.2 Hz. It's the lowest note of double bass and bass guitar. 

Your Bass Pedals are ready!

MIDI message conversion


Red dots on top picture shows original midi notes that needs to be converted to new midi note messages. Only those red dot marked keys are used on conversion and other notes are filtered out.

If you have malfunctioning notes on your keyboard you can change midi notes you use for conversion. For example low F can be C or E instead of D.

Conversion Chart

original midi note --> remapped midi note

37 --> 40
38 --> 41
44 --> 42
45 --> 43
51 --> 44 
52 --> 45
56 --> 46
59 --> 47
65 --> 48
68 --> 49
72 --> 50
75 --> 51
79 --> 52
80 --> 53 
85 --> 54
86 --> 55
92 --> 56
93 --> 57

Here is a picture that shows original midi note and remapped note number

Software options

I tried to find ways to remap MIDI notes that would work in different operating systems. 

VST plugins

If you like to use VST midi plugins there is a really nice collection of plugins called Piz MIDI. It's made by Insert Piz Here and it's should work on Windows, Mac OS X and Linux. You can download the collection from here

In the site there is a list of DAWs that will work with those plugins

You will need midiNoteMap and midiTranspose plugins from the collection 

I use Windows computer and Reaper DAW. 
I have only tested midiNoteMap with Windows computer but there is a strange bug at least in the Windows version. To work properly you need to put midiTranspose plugin before midiNoteMap and set transpose value to +6. For some reason midiNoteMap sees incoming notes -6 semitones off. But using midiTranspose to correct this is a quite an easy workaroud.  
If you find that midiNoteMap is working correctly in your system please let me know!

Here is a screenshot from Cockos Reaper. There is no GUI in midiNoteMap so every DAW shows it differently.

There is a slider for every MIDI note. You can set remapped notes with sliders.
Simply turn unneeded midi notes to far left. Then the value is '-' and the plugin filters out that midi note.

Pure Data


If you don't want to use VST plugins you can use Pure Data to manipulate midi messages.
You can download patch I made from here

PD bass pedals

Screenshot of Pure Data Patch

I use Midi Yoke in Windows to route midi between applications. There are instructions in the web how to do it on OS X. I don't know how Linux handles MIDI.

In Pure Data's MIDI Settings I set my hardware MIDI input as input device and MIDI Yoke as output device. I disable any input and output device in Audio Settings. It's important that you set Delay (msec) value to 0 in Audio Settings. If delay value is something else than zero there is latency in MIDI messages.

You can now route your manipulated MIDI messages to DAW or hardware synths. 

Happy playing!

Playing tip!

In some keyboards the keys are pretty high. If you play standing up it might help your playing if you use something to lift yourself a little higher from the floor.

Demo video of Bass Pedals in action

I used AAS Ultra Analog for bass sounds. The white keys are not yet covered with white plastic in this video. I made a setup that uses modulation wheel to crossface between two synth presets. Mod wheel also acts as a volume control for Valhalla Shimmer reverb (in guitar fx chain) that is set to octave pitch shift feedback effect.

The track I play is called One Hour Backwards.


I made also an Instructables-version of this project


  1. Nice hack, and great demo video!

    I'm not a musician, but based on the image of the Taurus, maybe it would be better to use something with a little curve to it for the "key spreaders". Seems like it would make it easier to hit one specific pedal without hitting it's neighbors. Maybe cut up old shampoo bottles or other packaging?

    Another thought: Here in the Midwest U.S., old electric organs show up all the time on craigslist or in the thrift-shops. They have a ready-made pedal board you could rip out and wire up to an old MIDI keyboard.

  2. Thank you very much! Yes, rounder keys might be even easier to play but this design is not hard to play. You have to look the keys though. Many people have hacked those home organ pedals. They are not so common here in Finland. And converting them to MIDI pedals is not so quick project. :)

  3. Thanks for share nice information here. Keep it up. i have wanna share one blog and me hopeful you check my blog plastic and sheet metal product manufacturing.

  4. Great hack! thanks for sharing, I just have one doubt, hope you can help me with it:

    Im new to synths and MIDI controllers, so let me see if I got this right. Once you do the MIDI note conversion to the keyboard, can you route it directly to another synth, lets say a Juno 106 with MIDI ins an outs, (thats the synth I have) and control it with this MIDI bass pedal keyboard? or do you always need to have a computer involved?

    Thanks again, greetings from Mexico!

  5. Thank you very much! Unfortunately you have to use computer or some kind of midi converter to convert midi note mapping. If you have a hardware sampler you can map bass samples like that midi note mapping.

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  7. Great Project !!! I'm almost done with it....Will be very cool !!! Thks for that awesome instruction sheet !!! Btw, I have made 2 projects on my they are...... 1st : (crappy noise has been fixed...was my PC output)


    THKS, Pat

  8. I have hacked my old keyboard...Download both VST (midinote and miditranspose) brougth them into my CUBASE....followed all steps you mentionned up=here...but still not working....It's like PC cannot talk to keyboard,or verse-versa...any advise ????

  9. Hello! Is it the first time you use MIDI plugins in CUBASE? I'm not CUBASE-user but maybe there is some configuration that needs to be done before MIDI plugins work. Try to google.

  10. MIDI bass pedals like 12 step by Keith McMillen is more reasonably ...

  11. Very cool!