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How do I subtractively synthesize a tanpura drone and its timbre?

The tanpura has 4 strings (Basic notes of Tanpura). The first is tuned to a fifth or some other note, the next two are tuned in unison to the tonic, and the last is tuned an octave away from the tonic.

What is the strategy for mapping these strings to 3 oscillators? Use a light chorus on the two tonics? Use an octaver to map the last string an octave down from one of the tonic notes? Do a second pass on a looper or delay with a second preset?

How do I capture the distinctive timbre of tanpura drones? (https://ragajunglism.org/tunings/tanpuras/)

I have a three-oscillator subtractive synth (BOSS SY-300, but the answer would generalize to most 3 osc. synths) and a looper, and I'd rather not pay even more money for an electronic sruti box. I've got enough gear on stage as it is.

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  • Maybe giving the exact model of the synth could help provide more exact answers !
    – Tom
    Commented Apr 21, 2023 at 8:20
  • I realise you're not asking for instrument recommendations, but Roland have several that would fit the bill - including sound cards, should you happen to have a synth which would take them.
    – Tim
    Commented Apr 21, 2023 at 8:26
  • BOSS-SY300 is polyphonic, isn't it? You don't need to assign an oscillator to each string of tanpura, you can just play the right notes? Commented Apr 21, 2023 at 17:57
  • @user1079505 not sure. Two of the notes are unison so there might be interactions between the strings that I'm not aware of.
    – empty
    Commented Apr 21, 2023 at 19:32
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    On the other hand, the individual strings are typically plucked in succession, rather than strummed together. But maybe this can be automated with LFO? Commented Apr 22, 2023 at 5:34

4 Answers 4

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Ok, interesting question. You may be able to approximate that sound somehow, but won't match it 100 %.

I refer to this manual: https://static.roland.com/assets/media/pdf/SY-300_ParamGuide_e02.pdf

1 ) Let's have a look at the signal flow the BOSS provides:

  • the green path is your guitar signal with all its spectrum of a string
  • the red path is the buit-in synthesizer, i.e. your string signal just triggers the selected wave form (pulse, sine, ...)
  • close to the output you can mix the two, which is a kind of layering
  • THRU/RETURN are just needed, when you want some external effect processing

signal flow

2 ) What do you need to achieve? Let's have a look at the time-dependent spectrum in the link you mentioned: spectra

Let's simplify and look only at the fundamental in both diagrams (undotted red). In image a it just decays over time:

  • trigger osc=sine
  • next, you'd need to apply an ADSR unit on the output amplitude, to DECAY the amplitude (and it has to happen AFTER triggering the internal synth)
  • and there you're lost, unless I oversee something in the manual:
  • it just provides ATTACK for the AMPlitude, no decay, sustain, release
  • but you may be able to (ab)use the FADER unit for this purpose

Mimicking the fundamental in image b is even harder, because you may modulate the amplitude by a LFO (if the BOSS allows that), but it needs some delayed onset.

3 ) Now, in an ideal ADDITIVE world, where you have 14 SINE wave OSC available, which you can set in pitch individually (integer multiples of the fundamental) and can assign 14 ADSR's individually, modulated by 14 LFO's, you may come close to the desired Tanpura sound and droning.

4 ) But not all may be lost, applying some simplifications.

4a ) Because the spectrum list 1, 2, 3, 4 ... multiples of the fundamental, try a saw or triangle wave, which has a similar spectrum.

4b ) Filter should be set to a wide pass, i.e. a low-pass with very high cut-off. Try mimicking the amplitudes DECAY, e.g. with the BOSS' fader. If possible, vary it by some LFO.

4c ) Mix red (synth from 4b) and green path (your guitar input). I.e. mix two different sound characteristics.

4d ) Perhaps it's useful or necessary to repeat 4a, 4b and 4c for 3 SAW/TRIANGLE OSC's, with different (bandpass) filters and different LFO-frequencies, to mimick what happens on the Tanpura. Perhaps it's useful to run one of them as PULSE/RECTANGLE, which produces a more hollow sound (multiples of 1, 3, 5, 7, ...). (Also the ring osc may help here and there, if set correctly // it has plenty of bad effects, but sometimes very nice ones)

4e) Wrt the green path perhaps some preprocessed guitar signal is useful.

5 ) As a rule of thumb, FX (effects) is to sound, what make-up is to a face:

  • you can hide a little
  • you can highlight a little
  • but you can't change the face (i.e. the sound characteristic in itself)

So, chorus, phasor and what have you may make the final sound more "sweet" or interesting, BUT the basic ingredients must be provided first, as described above.

6 ) If in doubt, try less:

  • switch of all FX in the beginning anyway
  • reduce the number of variables (i.e. kick out the 3rd OSC etc.)
  • balancing amplitude levels will be (almost) half the job
  • if it doesn't work out today, retry tomorrow with fresh ideas and new overnight experience

7 ) What sometimes works out nice on my synth-keyboard is to overlay an attenuated pure sine over some complex synthi-sound. Depending on its fundamental it can add some otherwise missing crisp or metallic nuance. (Try perceiving your guitar signal OR its THRU/RETURN processing as the way to go this route.)

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  • Thank you for your thorough answer! How would you suggest mimicking the twang and buzz of the tanpura?
    – empty
    Commented Apr 23, 2023 at 20:19
  • Thanks, You’re welcome. // As I tried to line out it‘s a matter of small frequency deviations, just like we know from beats or cars turn signals. That‘s why LFOs should be similar, not the same. IF it‘s possible to mimick twang and buzz with the BOSS, key will be level mixing, i.e. amplitudes. // Perhaps it‘s better to forget about the Tanpura for the moment and trying to create drone like variations first. It‘s a learning process. Perhaps the biggest drawback is missing ADSR functionality.
    – MS-SPO
    Commented Apr 23, 2023 at 20:54
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Here is yet another option to cpme closer to your goal quickly. Video Boss SY300 Synth Pedal No Talking shows at 06:40 preset "P35 Throat Chakra", which sounds much like what you probably want.

video

Some ideas what you can do with it:

  1. use it, because you like it
  2. tune in this preset, check all parameter settings; take notes, try to understand the important issues
  3. repeat for other presets; make a list, table etc. so you can learn about the way they did it with this device (it may have some hidden technical gems inside)

So far I didn't find a website, which already did this job. May be, there even are programs which makes retrival and manipulation easier (via USB). E.g. for my keyboard there is a community of freaks, who did it. Perhaps sth. similar exist for this device?


Ok, here are two videos from Austin Sandick, product specialist at BOSS. The videos show both features, close to what I lined out in the application of the strategy, AND ... limitations by this synth. However, these are the knobs and pages, you want to understand better.

This video talks about the LFOs , most interestingly after about 05:00. This video talks about filter and amp ; again, after the middle it becomes more interesting; fading was mentioned somewhere, probably in the beginning.

So either you can mimick my SINE and TRI approach more or less. Or you can combine two TRI with the SINE, where both TRI vary filter and amp by similar LFO-frequencies. Should be possible, to obtain sth. useful.

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    youtu.be/uhLr7k7Vj9A?t=403 is very close. Thanks!
    – empty
    Commented Apr 24, 2023 at 18:15
  • Great :) // Right: know your device, know your technology, know your goal.
    – MS-SPO
    Commented Apr 24, 2023 at 18:16
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I take liberty to post a second answer, which is an application of the requested strategy https://music.stackexchange.com/a/129621/88467 . It's intended to further guide the TO through the technical features of the BOSS SY-300, indicating what to look for, to try or to mimick as close as possible.

PRELIMINARY NOTE: If somebody please can hint me to a free, login-free storage for audio files, I'm willing to create and upload some sound demos for this setting, later. Thanks

NEW NOTE: Please find a link to demo-sounds at the end of this answer.

Because I neither have the BOSS SY-300, nor an electric guitar, I used the synthesizer stage of my Nord Stage 3 keyboard to replicate the requested sound, somehow.

With every stroke of my keyboard it triggers 2 synthesizers A and B, which are configured like below.

First, let's have a look at the signal path, the red lines. The keystroke triggers a SINE in A, a TRIANGLE in B (I started with a SINE as well and later switched to TRI). This signal passes the filter, which varies a little and finally the amp, which modulates its gain (amplitude).

layers A and B

Second, both use a LFO, set to two different frequencies. TRI means, it just moves its signal up and down, like turning a knob left and right. (In fact, it's a kind of automation synths provide.)

The LFOs are used to change parameters: resonance frequency for both, and also pitch for A, to quite a big amount.

Let's have a look at the filter. The simplified curve shows:

  • it's a low-pass, which cuts off at some f_res
  • it provides a self-resonance at f_res
  • the LFO shifts f_res a little left and right over time, "slowly"
  • as a result, it varies the preceived sound of the OSC used to some degree.

For instrument A, with the sine, varying the filter seems to be quite pointless: it's a sine after all, 1 frequency. HOWEVER, the SINEs pitch varies a little, though set to 0, resulting in overtones, creating a kind of gurgling sound. This is ONE part of the Tanpura approximation.

(The TO could well use his guitar and the green signal path indicated in aboves link, as his instrument A, with or without pedal effects as input.)

filter

Finally, let's have a look at the AMP stage. The following diagram indicates, how the AMP changes its gain via an ADR within the about 14 s after triggering A and Bs Oscillators with every keystroke:

ADR

If you listen to instruments A and B separately:

  • A sounds a bit like a xylophon, dimming away in 3 s
  • repeated keystrokes let A sound a bit like in an echo chamber (different, but a bit like with a looper)

While

  • B sounds quite nasty
  • it takes a little to become strong (A)
  • fades away in about the next 9 s (D)
  • and still fades away after release of the key (R)
  • slowly varying keys superimpose in time very Tanpura drone like sounds
  • and because the LFO varies both filter resonance and sound spectrum, it gives rise to beats simular to the wanted ones, see wikipedia

Now, A and B provide many of the Tanpura characteristics I mentioned in the strategy link above.


A few words on play-ability.

On a keyboard I can both play chords (e.g. left hand) and melody (e.g. right hand). This may be quite restricted with a guitar: probably the BOSS will trigger on the chord signal as a whole, rather than on 3 or 4 keystrokes my left hand may provide.

It seems to be effectful, to keep some notes to let the drone (instrument B basically) develop. I.e. the way you play is more or less "dictated" by the ADR-unit, less by a note sheet.

As you may guess, at least for instrument B the ADR-functionality is vital to approximate a Tanpura effect.


P.S.: Though aboves result are already quite good, a little more is needed, which, unless I overread something, is beyond the capabilities of the BOSS SY-300. Let's have a look at the modified instrument B*.

Recall or note, that the filters cut-off frequency is determined by an internal voltage (so parameter f actually is a voltage u_f).

modenv

Offset to this DC-voltage is the triangluar wave, created by the LFO; "amount" basically sets its amplitude. That's how the filter moves its characteristics up and down the frequencies with a rate of 192 Hz.

Now, we need to add an other offset. With every keystroke (on my keyboard) or every trigger (inside the BOSS) an other ADR-unit creates a pulse like given above. Only this time it's just another offset to the internal f-voltage. Setting D = R ~ 1 s seems to give nice twangs. This ADR:

  • shifts the filters f even a bit higher (A; short)
  • then lowers the filter frequency again (D)
  • and still lowers after releasing the key (R)

Please open this link in a new window to listen to the sounds. Screenshot of said page:

linked page

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  • 1
    An even better answer; maybe you could merge the two answers? As for login-free and free sharing sites that store media, that's tough. All the login-free sites I know delete your files after a period of time. You could put it up on Google Drive for free. Your other files will be safe.
    – empty
    Commented Apr 24, 2023 at 17:51
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    Ok, found a solution. Please follow the link at the end of this answer to listen to the sounds. The BOSS will sound different, but you probably can catch some of the Tanpura characteristics in a similar way.
    – MS-SPO
    Commented Apr 25, 2023 at 20:12
  • It's close, but it needs to be shifted down in pitch by a couple of octaves, I think. It's a great start!
    – empty
    Commented Apr 25, 2023 at 20:45
  • That‘s simple: move to a lower octave. The purpose was to show direction and relevant effects.
    – MS-SPO
    Commented Apr 25, 2023 at 20:59
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Ok, some finalizing answer to your request, i.e. a strategy, which I demonstrated practically.

Remarks on synthesizers

Synthesizers, even when using similar components like SINE-osc and filters, come with their individual tonal sound impression.

The technical approach the SY-300 takes is very old: using basic waveforms together with filters and LFO's exist since the days of Moog, Oberheim and others.

For maximum flexibility people use modular devices, so they can manipulate their control signals (low frequency voltage waveforms) to their likening, like in this short video and in this longer one. Watch the differnt approach to playing ... (You find replicas of this approach in many SW-synths)

New approaches, like my Nord Stage 3, provide Pulse Code Modulation (PCM), which is a fancy techno-slang word for "using samples". enter image description here

So ... using a synth can only mean to use its tonal effects within its technical limitations for musical purposes. The sooner you say good-bye to true replication with a limited technology (SY-300), the earlier you can discover its hidden gems for you.

True Tanpura Synths

They use PCM, of course. Here's the Roland GR55, which you certainly know, and was hinted at in a comment before:

  • all (western oriented) presets (video) // this you probably don't need
  • extension for Indian Tones (video) // this is your desire; sales address given there

Re-discovering your SY-300

I added "Mixing Guitar with Twang-part only" to the extra-site given before. It:

  • simulates routing a Classical Guitar through your SY-300 (green path // see Signal Flow in previous answer)
  • simulates using only a twang-part (instrument B*) to augment the tonal impression, i.e. using exactly ONE osillator
  • assumes internal mixing

Note:

  • the twang part is as-is, i.e. it does not adjust to the key pressed / pitch played (I can do it on my keyboard, but the SY-300 doesn't seem to provide that)
  • if you want it sound deeper, lower f-cut-off
  • the SY-300 won't replicate B*, but you can produce a similar effect

Final

Enjoy rediscovering your SY-300. As I wrote, it's not bad, if you know and operate within its limitations.

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