MOTM

>I won't copy and paste everybodies posts to keep from making a mess. I'll 
just 
>respond. Larry Hendrey missed the part where I said I wanted to remove a 
string 
>and in its place put some kind of device to vibrate the bridge. That would 
>vibrate at whatever pitch my synthesized waveform is. So matt_stubb and 
>groovshaman are correct in understanding what I wanted to do. I would need to 
>keep the other 3 strings there to firmly hold the bridge down, plus in all 
the 
>reading I've been doing about the violin, the body tone is a little different 
>when under the tension of all the strings than without any strings. Without 
>strings the main formants are lower in pitch.

>When I thought of doing this a couple of years back I thought maybe I could 
>just screw a speaker into the back of a violin body. It's hard to tell if 
that 
>would give me any useful results or not. Based on what I've read, the bridge 
>acts like a lever and where it rests on the violin body and it's internal 
>structural supports determines where or how strong some of the main 
resonances 
>will be.

>I'm looking at a small speaker now and there's the possibility if I cut off 
the 
>speaker cone I could use the transducer portion of the speaker to vibrate 
>something. I don't know how I'd mount it to the bridge, but maybe I could 
>compromise and remove the bridge and strings and mount it where the bridge 
was.

>-Elhardt


>The nature of a piezo will not let it produce enough energy.  I think you
>need something with a coil in it.

>To rectify my error, I will report to you that All Electronics has a
>"vibrating audio transducer" designed to "make a wall, door or other object
>act as a speaker" for $9.00 in their catalog.  Check out part # AS-500.
>Probably at their web site too. Now, I feel better.
>LH

Y'all are probably already thinking this but nobody's actually said it, 
so I will. If you use a speaker in any way, you will always hear the 
speaker, probably more than the cello or whatever resonant body you are 
using. It seems to me that what you are looking for is to use the cello 
not as a reverberant chamber for sound produced by a speaker (it's not 
big enough for real results), but to use the cello body itself for your 
speaker. To achieve this, Larry's transducer sounds like a good bet. If 
it's designed to resonate a door, it should have plenty of amplitude. 

You could probably mount it anywhere on the cello and get varying 
results, but if I were to do this, I would start by mounting it on the 
bridge. If there were a way to do it, I would actually try to mount it so 
it was pushing down on the bridge, toward the body, so as to emulate the 
strings as closely as possible. Be aware that each part of the cello 
plays a part in amplifying the sound of the strings. The bridge has that 
funny shape because after years of experimentation, the builders found 
that it was the best design for transferring the resonance of the string 
to the body of the cello, and the body is designed to optimally amplify 
vibrations from the specific location of the bridge. 

Perhaps you could mount the transducer on a surrogate bridge; the most 
important parts would be the feet, to match the locations of the original 
feet, and maybe grooves for the strings, to hold it on. I would avoid 
screwing anything onto the body because it significantly decreases the 
resonance. The best sound transference occurs when the resonating contact 
point is under pressure, not held on with screws. Also, as someone else 
said, watch out for the soundpost inside the body; it's not glued in 
place, and if you remove the bridge it can fall out, reducing the 
resonance by more than half and weakening the top of the cello so the 
tension on the bridge can crush it. When I change the bridge on my bass, 
I lay it on its back and put a couple of large books near the bridge to 
keep pressure on the soundpost.

Tune the strings according to whether you want string resonance or not 
(minimal resonance if you tune Eb for a tune in D), or to whatever notes 
you would want to ring. If you want no string noise, you can put a rubber 
band loosely around the neck and strings. I would imagine that it would 
be most effective amplifying music in the natural range of the cello. 

I've mentioned this before, but I have a book called "Synthesizer 
Technique" (Hal Leonard HL00183706) which is all reprints of Keyboard 
Magazine articles from the '70s and '80s, many by Bob Moog, Patrick 
Gleeson, Roger Powell, and Craig Anderton. Moog has a couple of articles 
on using filter banks to simulate the resonances of string instrument 
bodies.

**************
>BTW, along those lines. I ran into a guy once who has brass trumpets for his
>horn drivers.  This was back in the early digital days before good sampling.
>He used them to play his brass patches through these.  Even though they were
>only DX-7 brass patches, they sounded so realistic because the horn
>contributed so much to the sound.

Very cool idea. The hugest church organs have ranks of trumpet pipes, and 
when they crank up the sound is terrifying.
*****************
>I think this is going about it the wrong way.
>More complicated, but more controllable is to get a mechanism to "push & 
pull" the bow 
>across a string. Not a regular bow, a small one (say 4 inches). I would do 
this:
>Paul S.

Mechanical string instruments such as the hurdy-gurdy don't use bows, 
they use rotating wheels rubbing on the string. Much easier to control 
than a bow, and you don't have to worry about running out of bow. Seems 
like I read something about rosined leather wheels.
******************


>And to expand on this idea a little further: I plan to tune the
>strings on the guitar to an open tuning (say, Open D) and then play a
>sequence in the same key through the thing.  I think the acoustic
>drone of the strings will add (if I can believe what I'm hearing in my
>head) and incredibly interesting background.  I just hope the strings
>don't overwhelm the sound from the synth, but we'll see...
>Mike

>Go play a piano with the sustain pedal depressed. It's essentially the same
>thing. Not only to the struck strings sustain, but the rest of the undamped
>strings also resonate. In fact, a patent was filed for a reverb system based
>on this. I remember reading about the patent just after I'd come up with the
>idea myself, probably in the early '80s.
>CGS

I've got an old piano soundboard with the strings attached; the rest of 
the piano was hacked off. I love to play sounds into it and listen to the 
reverberation it generates. I've been thinking of mounting a couple of 
PZM mics under the strings and using it as an "analog reverb unit". 

Frank Zappa did a project long ago in which he recorded people talking 
from inside a piano; he says he actually had them climb into the piano 
and rap. The idea seems to have been to see  how the piano would mutate 
the conversations.

nathan