One of the cooler projects I've ever done was for Trimpin's "If VI Were IX" robot guitar installation at the EMP, which is now call the Museum of Pop or MoPop.
Photo is by Thomas Upton who was nice enough to license it under the Creative Commons license. A higher resolution version from Mr. Upton is available on flickr.
The giant whirlwind looking collection of instruments in MoPop shown in the picture above is actually a guitar robot. You can see various guitar-ish looking items with rows of devices lined up on either side of the guitar fret board. These are the guitar robot elements. A little above the center, slightly to the left, the purple and blue-ish guitars are both Trimpin's custom build guitar robot elements.
Each element has a single string, a "plucker," and "frettles" which are the devices lined up along the fretboard. These are solenoids and when you apply voltage to their coils they pull the solenoid closed, which pushes a pad down on the guitar string, one device per fret.
Each string has a controller - well, two for now, one to control frettles and one to control the plucker. A MIDI input is routed to all of the controllers, and groups of 6 pluckers and their associated frettles are assigned to a single MIDI channel as a logical guitar. The mapping from MIDI notes to guitar frets is odd since we skip octaves between strings so that each fret on each string is a unique note. This means that the MIDI played on the robot guitar has to be processed to put notes into artificial octaves (incorrect musically) so that each note can only be played on one specific string, making the control easier to implement.
Trimpin made a second generation version for his own use that was simplified and improved. The plucker controller now also controls the frettles fot the string it plucks. The quality of the sound degrades as youi move up the frets - by 7 it's tinnier, by the 12th fret it sounds lousy - so in the second version Trimpin only provides 5 frets per string, and adds more strings to handle multiple notes simultaneously.
We also added a damper - a soft pad that rests on the strings, damping them so that a plucked note ends very quickly. When a note goes on, we lift the damper for that string, and when we get the note off command we drop the damper back onto the string. If a note-on is followed by a different note-on for the same string, we switch frettles and keep the damper up.
We modified our response to MIDI note-on commands so that low velocity notes (below 12% of full velocity) do not actually use the plucker, they just keep the damper up and deploy the correct frettle. This allows for hammer on and hammer off techniques - playing notes by hitting frets with the left hand, rather than using the right hand to pluck.
We also added a mode where you can switch off the dampers, so they stay damped the whole time. This allows for a different sounding result - notes are brief and a little muffled,
Using MIDI commands the new generation control has a wider variety of options and sounds available. Trimpin has used the second generation guitar robot control in live performances from time to time, but I dob't think there's a permanent installation using them yet.
We're hoping that the EMP will want to replace the current first generation controls with a 2nd generation control (or by then probably a 3rd generation since we'll most likely add a few more tweaks). We've looked into the devices needed - our original microcontrollers are no longer available new, and using surplus used devices is dicey at best, so we'll be changing microcontrollers and tool sets if we get to do this work.
I hope we get to do it, I enjoy working on robots and robotic guitars are one of the more interesting robots I've ever worked on.
The giant whirlwind looking collection of instruments in MoPop shown in the picture above is actually a guitar robot. You can see various guitar-ish looking items with rows of devices lined up on either side of the guitar fret board. These are the guitar robot elements. A little above the center, slightly to the left, the purple and blue-ish guitars are both Trimpin's custom build guitar robot elements.
Each element has a single string, a "plucker," and "frettles" which are the devices lined up along the fretboard. These are solenoids and when you apply voltage to their coils they pull the solenoid closed, which pushes a pad down on the guitar string, one device per fret.
Each string has a controller - well, two for now, one to control frettles and one to control the plucker. A MIDI input is routed to all of the controllers, and groups of 6 pluckers and their associated frettles are assigned to a single MIDI channel as a logical guitar. The mapping from MIDI notes to guitar frets is odd since we skip octaves between strings so that each fret on each string is a unique note. This means that the MIDI played on the robot guitar has to be processed to put notes into artificial octaves (incorrect musically) so that each note can only be played on one specific string, making the control easier to implement.
Trimpin made a second generation version for his own use that was simplified and improved. The plucker controller now also controls the frettles fot the string it plucks. The quality of the sound degrades as youi move up the frets - by 7 it's tinnier, by the 12th fret it sounds lousy - so in the second version Trimpin only provides 5 frets per string, and adds more strings to handle multiple notes simultaneously.
We also added a damper - a soft pad that rests on the strings, damping them so that a plucked note ends very quickly. When a note goes on, we lift the damper for that string, and when we get the note off command we drop the damper back onto the string. If a note-on is followed by a different note-on for the same string, we switch frettles and keep the damper up.
We modified our response to MIDI note-on commands so that low velocity notes (below 12% of full velocity) do not actually use the plucker, they just keep the damper up and deploy the correct frettle. This allows for hammer on and hammer off techniques - playing notes by hitting frets with the left hand, rather than using the right hand to pluck.
We also added a mode where you can switch off the dampers, so they stay damped the whole time. This allows for a different sounding result - notes are brief and a little muffled,
Using MIDI commands the new generation control has a wider variety of options and sounds available. Trimpin has used the second generation guitar robot control in live performances from time to time, but I dob't think there's a permanent installation using them yet.
We're hoping that the EMP will want to replace the current first generation controls with a 2nd generation control (or by then probably a 3rd generation since we'll most likely add a few more tweaks). We've looked into the devices needed - our original microcontrollers are no longer available new, and using surplus used devices is dicey at best, so we'll be changing microcontrollers and tool sets if we get to do this work.
I hope we get to do it, I enjoy working on robots and robotic guitars are one of the more interesting robots I've ever worked on.
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