Conceptual desisn: Drone strings

[R.G.]

I've always liked the sound of the drone strings on a sitar. It struck me this morning that you could do a drone strings adapter to an existing guitar without modifying the guitar. Maybe.

The idea is to make a drone string mechanical setup - a batch of several drone strings on a (probably) wooden carrier, drive the carrier's base or bridge with a small speaker to shake the strings from an incoming audio signal, and then electronically pick up the drones' vibration with some pickups.

There are some reasons not to try making purely electronic drones,  I think.

I may tinker something like this when I get a bit of free time. Using an outboard setup lets you not modify the guitar, but still get drones. Using an amplified drive to the drones allows you to tinker with the drive level independent of the need for acoustic/mechanical coupling from the played string, and using pickups lets you easily adjust the amount of drone in the signal. Using mechanical strings lets you get the advantages and complexity of mechanical resonantors.

[PRR]

Why not just use another guitar? It gives the framework, the tuning-pegs, the pickup ready to go. Every guitarist has a 13th-best guitar that sits idle. Maybe a 2nd-best guitar stand also. It comes down to string-shaker and electronics.

[Mark Hammer]

Wound or unwound drone strings?  "Harmonic swirl" type sound, as on a sitar, or something more in the realm of steady oscillation of a purer wave form with maybe some modulation?

One of the things I always liked about the Boss DF-2 Feedbacker was that one could create a single drone note and hold it to play over.  The held note has just a touch of modulation to keep it interesting enough for a synthetic tone.

[R.G.]

Why not just use another guitar? It gives the framework, the tuning-pegs, the pickup ready to go. Every guitarist has a 13th-best guitar that sits idle. Maybe a 2nd-best guitar stand also. It comes down to string-shaker and electronics.

I thought about that, and it would be a quick and dirty way to go. I went to the separate string enclosure because in my mind I thought it would be useful (1) to have the possibility of more than six strings and (2) isolation from the surrounding racket on stage. I didn't think most guitarists would necessarily like it if someone else's guitar was moving my drone strings.

@Mark:
The idea of more than six strings was to allow a diverse set of strings. I envisioned maybe a dozen or two, with the ability to selectively damp each string, perhaps with a pushbutton damper setup. That would make it both more useful in real time when you're changing keys perhaps per song, and also allow you to mount a couple of sets of diverse string types.

I actually conceived this thing as a plywood box with the strings inside and some damping on the box so it's not just an acoustic pickup drone - although that's another possibility too. Perhaps your 13th favorite acoustic ...   

[Rob Strand]

The idea is to make a drone string mechanical setup - a batch of several drone strings on a (probably) wooden carrier, drive the carrier's base or bridge with a small speaker to shake the strings from an incoming audio signal, and then electronically pick up the drones' vibration with some pickups.

There are some reasons not to try making purely electronic drones,  I think.

Yes it's a cool sound.   I agree synthesized/electronic sounds will probably lose something unless you can do it in DSP with a string model.

You could even tweak the sound like putting paper under the strings and all that type of thing.

The coolest thing would be to build a miniature version.  When I look at fluids people they build small versions that scale all the parameters.  In their case they take the numbers and scale them back theoretically to interpret the results.    The equivalent would be to frequency shift-up the input signal, feed it into a smaller set of strings, then frequency shift the output down again.   If you used a multiplier it might even add it's own character.    The problem is getting the laws of physics to sound the same.   Probably have to mess with the length to diameter ratios of the drone strings and after that the damping might not be so great.

[samhay]

https://en.wikipedia.org/wiki/Harp_guitar has a brief section on electric versions and some of the stuff William Eaton looks interesting.

[GGBB]

[digi2t]

Gizmotron?

[Rob Strand]

2018 Definition:

[anotherjim]

My concept would look like a box of strings too. Some acoustic isolation would be necessary, but we have the materials. After all, didn't Wurlitzer build organs with a TOG consisting of continually blown reeds with electrostatic pickups? That had to be enclosed to stop the racket it would have made.

[aion]

Wound or unwound drone strings?  "Harmonic swirl" type sound, as on a sitar, or something more in the realm of steady oscillation of a purer wave form with maybe some modulation?

One of the things I always liked about the Boss DF-2 Feedbacker was that one could create a single drone note and hold it to play over.  The held note has just a touch of modulation to keep it interesting enough for a synthetic tone.

Check out the EHX Freeze or Superego. Nearly flawless note reproduction, and it works for either single notes or chords since it uses a digital sample.

I had a friend a few years back who was trying to figure out a way to put an e-bow onto an adjustable arm attached to the body of the guitar so he could hold it in place on whichever string he wanted to drone while he played something else. Then the Freeze comes out and basically does the exact same thing with the touch of a footswitch. He gave up his idea in a hurry!

[amptramp]

Go to page 52 here:

https://www.americanradiohistory.com/Archive-Radio-Electronics/60s/1968/Radio-Electronics-1968-05.pdf

which is the article on "vibrating-wire audio filter and oscillator" and you can see how to arrange for an electrical signal from the drone wires.  It covers all the harmonics that would be present in a vibrating wire if the magnet is located properly.  You take part of the guitar output and put it through the Wheatstone bridge filter network.  The Q of a vibrating wire is quite high - over 600 at 1000 Hz.  They used two transformers but a power driver like a 386 would enable you to eliminate the input transformers and the output could be taken from a differential or instrumentation amplifier for each wire.

This is the same article I quoted for the thread on sustain generators.  The filter behaves like a pickup on a guitar - the location of the magnet determines what harmonic content you have.

[anotherjim]

Or reeds. Can also be called "Tines". This kind of system was in use for decades by railways (may still be in some places). The problem was to electrically detect the position of DC powered trains. A system for that had to be immune from supply frequency AC and DC interference so tuned discrimination was required back when there was no cheap solidstate electronics to help. Both the power current and train detection had to use a common return rail so you can imagine what a problem this is. Reeds worked fine until even DC powered trains started using variable synchronous AC motor control. If you travelled in the power car of those trains, you can hear the power control frequency jumping as if changing gear - it is programmed to avoid interfering with the spot frequencies used in the reed train detection.

[noisette]

Are you aware of this?
https://tinyurl.com/yc9qc2bj

[Ben N]

I thought about doing this years ago; like so many projects, it never passed the thought stage. But same basic idea as RG's: some kind of a harp (I imagined it as having 12 or 13 strings, like a full octave on a piano, so there is something to resonate to every note; more strings might cover microtones) stretched across a box containing some kind of element to vibrate the strings, which could be electromagnetic like a Fernandes, or electromechanical, like piezos interfacing with the strings, or a speaker, which would also require the whole thing to be in an iso box; and an electromagnetic pickup, which could either be custom fabricated for that many strings, or cobbled together out of a couple single coils P-bass style. I still think it might be a very cool sonic enhancement.

[R.G.]

Well, it seems that I have once again invented something several decades too late!! 

The level guitar comes closest to what I had in mind. Actually, I thought the thing would be handiest if it was a base of maybe 12" x 24" plywood, with the bridge and nuts attached. The strings would be suspended about 1/8" above the base, and the electronics on a PCB mounted on a facing top ply.

Other than that, it's a many-channeled Ebow in a box.

Still thinking...   

[Knobby]

I've been lurking on and off for a while and had to finally sign up to comment on this thread. What you're after is the Voice Sitar, as used by the Incredible String Band on the song 'Invocation' from their 1970 LP 'U':

"A voice sitar is a flat board about 4ft long fitted with the same number of strings as the drone strings on a sitar and it includes an electric pick-up and a sending device, enabling you to feed any sound into the instrument, which will vibrate the sympathetic strings. The vibration is picked up and fed back out of the instrument. This is what was done with piano and violin on "Invocation"(U). Our voice sitar is the only one of its kind in the world and was made by an American named Greg Heat. We happened to hear it while in the States and asked if we could buy it."

This has intrigued me for years! The question is, what sort of transducer do you need to drive the thing and excite the strings? Presumably a standard guitar pickup could be used to recover the sound as you can obviously get 12 strings in the available width or we wouldn't have electric 12-string guitars. Would it be like an Ebow or sustainer, but with the sending and receiving parts separated, perhaps at either end of the strings?

Of couse, nowadays this sort of thing can be done with an EHX Ravish Sitar pedal, but I kind of prefer the idea of doing it in an old fashioned analogue come electro-mechanical way.

[anotherjim]

As used by Nicolas Collins in the link above, coils pulled out of miniature relays are a ready made source for the string drivers since they can be found made for the right kind of operating voltages and small enough to fit one per string. I suppose relays meant for 5v DC operation might be good for a single ended amp running from 9v.

[Nasse]

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My vote for external unit. I saw Nokie Edwards do a sitar medley and the borrowed axe was wthout drone strings

Blue reverb tank was less than 10 (or 20)

What If yo have a sitar bridge or jawari on drone strings

[noisette]

Hey R.G., what´s up with this? I´m really interested!

Nicholas Collins is quite approachable and helpful, I had a short mail exchange with him considering the countryman phaser once. I´ll ask him about the coils he is using and report back...