Electric Guitar => ChucK => Amp => Speaker

[Inventor]

I'm thinking of getting an electric guitar in July. It's March now, so I have a lot of time to plan, but a few months will go by quickly. Of course it is a requirement to route the Guitar into ChucK so I can do all kinds of fun stuff with it and post-process the sound.

What do you think is the easiest/best way to get the sound in and out of a Mac or a notebook PC, and what types of things would you do with ChucK in this application? Actually I never use the notebook, so that part isn't necessary.

Also I think I'd like to view the guitar's signals with my old scope as well, so I guess I need to make a little break-out box with the jacks and some terminals... Just thinking out loud... Suggestions?

[Kassen]

Get a soundcard with a pre-amp. Guitars (like microphones) need amplification to be brought up to line-level.

Cool things to try might be sampling it, looping that and playing a second part over it on the fly. Another cool thing might be analyzing the signal for pitch and re-synthesizing based on that.

Both of those techniques are available in guitar pedals as well but unlike distortion/compression/flanging/etc they leave a lot open for interpretation and going beyond the ordinary.

[Inventor]

I have an eMac, so there's no way to add a sound card, but there are interface thingies like this:

http://store.apple.com/1-800-MY-APPLE/WebObjects/AppleStore.woa/wa/RSLID?n=io_devices&fnode=home/shop_mac/mac_accessories/music_creation&nplm=TB084LL/A&mco=6843D59D

which are made to connect a guitar to the Mac. That one is $100, which is about what I'd expect to pay for such a gizmo. It comes with software, but would I be able to connect such a creature up to ChucK? There are other brands as well. Would I use OSC to establish the connection?

I like the idea of analyzing the signal for pitch and then doing things with that, plus the looping sounds fun. I'd like to do something original or new if possible. Once the pitch is detected, I guess it would be easy to play another instrument from ChucK's STK at the same pitch. Or I could create a variety of existing stomp box effects in ChucK. There are lots of creative possibilities, but I guess I won't know what's practical until I get there.

Patiently waiting for July (that's when my annual patent royalty check arrives)... It's not much in terms of dollars, but every little bit helps and it's satisfying after all those years of effort to actually get a royalty for inventing something.

[Kassen]

[kijjaz]

Yes. I also recommend that kind of audio interfaces.

If you don't have an audio interface, a tube preamp is good also.
(then connect from Tube Preamp to line-in of the onboard soundcard)

There are like millions of ways we can think up to play with live guitar...
Like making effects, doing delays, etc...

But this thing is what I recommend to try out:
Feedback.

That means the sound of the amp is loud enough to vibrate the guitar body so that you can create some altering chaotic effect from altering patches in chuck.
that's very fun to do.

maybe you might want to combine with prepared guitar also.
- - -

Hahahahahah..
it's more to the experimental zone.
i was playing an acoustic guitar plugged into chuck
and what I was using is reverb and some comb-filter with feedback.
it can be very beatiful and nice for ordinary audiences wanting to hear some pop or beatiful tunes.

having a sub-mix handy is gonna be great also.
so you can plug in guitar directly to the mixer,
"send" by aux of the mixer to chuck then back to mixer,
then connect mixer to amp.
with that, you can control the amount of effect quite comfortably during performance.

[radarsat1]

Miller Puckette gave a presentation at the Pd conference in Montreal about filtering his guitar down to a single partial and running it through a hilbert transform to convert the oscillation to a phase value. Then he used the phase to drive other types of synthesis. Pretty fantastic.

He had to build a custom interface to digitize each string seperately do it though, so it's gonna be some hardware work as well as software..
But you might get some cool sounds even out of the polyphonic signal.

[Frostburn]

[Inventor]

You'll hopefully pardon my ignorance of music and math terminology, but what do you mean by a partial, a Hilbert transform, and a phase? I think I have the background to understand what you're talking about and work with it to some extent, but I'm unfamiliar with the definition of those terms.

[Frostburn]

A loose definition for a partial is a time varying sinewave.
A sound can be seen (and heard) to be composed of many such partials.
You can in principle produce any sound by just summing up the output of many SinOscs but in practice this only works well for more pure sounds. The technique is called additive synthesis.
To get a partial out of a sound signal you can use a bandbass filter. (Only works if you already know the frequency of the partial and that frequency doesn't change, the general case needs a more technical treatment. I use FFT to get the frequency and fractional bin IFFT to do the additive synthesis.)
Partials whose frequencies are integer multiples of a common base frequency are called harmonics.

Phase is just the place where you are at the sinewave curve.
In the formula y = sin( x ):
x is the phase.
The concept of phase applies to any periodic signal. And in ChucK it's always normalized so that when the phase travels from 0 to 1 you get one period of sound from an oscillator.
So in chuck output = sin( 2*pi*phase ) for a SinOsc.

I haven't used a Hilbert transform myself but looking it up on Wikipedia it seems to do a 90 degrees phase shift on the signal (that is 0.25 in chuck phase). With sinewaves it's easy to extract the amplitude and phase once you get such a special pair for the sinewave.
Another way to exract the phase from a sinewave is to normalize it and use an asin function to get the phase. (You need take the slope in to account too, see Waveshaper.asin2() in my library).

Any signal can be broken down in to it's sinewave components but there are many ways to do that meaningfully.
One way is to use the Fast Fourier Transform. It has some length in samples, let's say 512 and it will break a signal down to 255 sine components and 256 cosine components. These sinewave partials are not always nicely aligned with the input signal and care (ie. windowing and overlap) needs to be taken.

If you're dealing with real functions you can calculate a fourier transform that can be seen as infinite collection of complex sinewaves (e to the power of i times omega). It's an integral transformation and it cannot be done exactly on discrete and finite signals like sampled sound.

[Inventor]

Thanks for the explanations, Frostburn, I already knew some of that and the rest was informative. I didn't know ChucK used 0-1 as phase, I'll have to change the upper limit on Synth Lab's phase sliders from 2 pi to 1. Also, phase seems to have multiple meanings in music. There is also the phase of a song, varying from 0 to 1 with the duration of the song. Plus I was trained as an engineer to recognize phase as a phase-shift, where the sinusoid is described as sin (2 * pi * f + phase), or was it sin (2 * pi * f - phase)? Doesn't matter, I quit engineering for good and I'm glad I did.

The method that radarsat1 described reminds me of some code I wrote for Acoustic Interloper, a fellow electro-music.com forum member, when I first got started with ChucK. He wanted to detect the frequency of his note plucking on the banjo and then use that frequency do something musical. In that case we were detecting an LFO-type signal in the neighborhood of five to ten Hz.

I'm looking forward to doing such things with Guitar Lab and Synth Lab once I get done optimizing them for speed. All in good time.

p.s. Like my new sig? It's one-line ASCII art!

[Inventor]

I've been reading and shopping online and have found some solutions.
The sound card that I like is actually a very low-cost, miniature one - just
right for a laptop. It's made by Behringer and sells for $29. It's their
U-Control UCA202 USB audio interface - but I will have to look into that
further as there is no mention of a preamp.

For a guitar I like the entry-level Fender Stratocasters. I looked at the
entry-level Gibson Les Pauls, but then I read that Les Paul actually had
very little input to their design - in fact some of his ideas were rejected.
The Fender has excellent sound and a whammy-bar which seems like fun,
plus dials and a 5-way switch for the three pickups. I don't know whether
to get the one with a humbucker pickup or the one with all three single
pickups yet. These guitars sell for $400, so they are a bit pricey but within
the range.

I looked at the USB guitars from Behringer, which have a direct USB
output to the computer which I really like. The problem is they are $120
guitars and I read some poor things about their construction.

I like kijjaz's suggestion of getting a tube preamp because that way I can
run it on overload *prior* to receiving it in ChucK. This would be a nice
option compared to a tube amp or tube-simulating amp on the output as I
would probably not want the tube distortion on special effects like thunder
and rain. Plus it would look way cool sitting there glowing next to the
computer with the tubes exposed... I bet those aren't $29!

Then I'll need a ton of accessories: guitar stand, guitar strap, picks, tuner,
etc. Oh, and I must not forget: the amp! I like the very low-end Fender
model for under $100, or a couple of notches up from that one. I don't
need a huge 75 Watt amp as that will only aggravate the neighbors! Just a
simple little one will do fine.

I'll keep you posted on my research as it gets closer to July. Gee,
Christmas in July, I can't wait!