[islandlabs] How to: Play Guitar Hero with a Real Guitar

Peter Williams petertw at gmail.com
Mon Mar 9 14:30:18 EDT 2009

some more thoughts on the non-hex-pickup version of the guitar project:

If you hold down a single string, it's easy to determine which fret &
string are touching by putting a voltage on the pick, and measuring
voltage on the strings and frets. (Except maybe when you pick it might
cause the string to temporarily contact other frets; we'll have to try
to find out.... Also, most electric guitars have metal bridges so all
the strings are in electrical contact with each other, but we can try
with an acoustic.)

If you hold a chord, however, most strings become interconnected
through the frets so it's much harder to determine which fret the
currently plucked string is contacting, or even which string is being
plucked. But maybe we can measure the resistance to determine which
string & fret are closest to the pick? If we could somehow increase
the resistance of the contact between string and fret that might help.

It will be fun to try anyway... :)

In the end we might have to build our own fretboard with multi-piece
frets (6 sensors per fret) so that the voltage doesn't carry from one
string to the next


On Tue, Mar 3, 2009 at 2:51 PM, Jim Robert <jim.mixtake at gmail.com> wrote:
> you could probably clip a piezo to your headstock or bridge and use it as a
> pickup... They work very well for this type of thing, and there are some
> clip on guitar tuners that use the same concept.
> Then use a lowpass filter to get rid of as many of the upper harmonics as
> possible...  (circuit to make a lpf here:
> http://en.wikipedia.org/wiki/Low-pass_filter)
> then get the frequency using an fft, and calibrate the system to which
> frequency to use at each fret (or just get the lowest one and use a little
> math to calculate the rest)
> Voila :)
> I think that calibration is going to be inevitable since you can't count on
> a guitar to be perfectly in tune (and even if you can, you can't count on
> your pickup to work exactly the same on every guitar OR that the frets will
> be perfect. Also, most people will not be using pro level guitars, and small
> inaccuracies are very common
> you may also want to add a function that keeps track of the pitch of the
> last 20 notes and calibrate the system on the fly to keep loss of intonation
> in check, which happens naturally as you play no matter what you do.
> One more idea about detecting strums... I would use amplitude to do this...
> many guitar players (myself included) rest their hand on the strings to mute
> them and accidentally touching the pick to a string would happen all the
> time.
> This is a really cool project, I'd love to be a part of it. Maybe jonathan
> will let me do another blog post ;)
> Jim
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