I've just released a free app for iOS called Samvada that uses Pure Data, through libpd and pd-for-ios. It's meant to simulate sympathetic strings, like on a sitar, for practicing and performing Indian music. It's also fun for other uses, and the strings make a nice resonance turning background sounds into tones. You can watch the demo and download it here:

Samvada for iOS

It's basically a bank of Karplus-Strong resonators. The UI handles the tuning aspects, which are aimed at Indian musicians using a drone and the Sa Re Ga Ma system of note naming/notation.

I'd welcome any feedback or questions about the process of making an app like this, etc.

Enjoy!

First, thank you for creating this app, it does exactly what I have been looking for. I am a musician that has long used filters and resonant strings to create new tones while I play. I also play the dilruba. There are a few things I would suggest for the app to make it even more amazing!!

First, if it is possible to add Audiobus support, at some point in the future, it would be greatly appreciated.

Would it be possible to add "just intonation" to the list of tunings? Perhaps some other non-western scales, as well, like slendro and pelog for gamelan?

In the spirit of experimentation, is there a way to change the wave that is used to generate the tones, like different presets for saw, square, sine, etc. without getting to modular?

MIDI control of the plucking strings would be pretty awesome as well.

thanks!!! and great job!!

Colorplates

I'm glad you enjoy using Samvada! I also have a dilruba, though I don't play it much. My main Indian instrument is the bansuri - I made Samvada to help me get to grips with Indian ragas on that.

You are not the first person to ask for Audiobus support - I have a copy of the SDK and am looking into it.

Re: "just intonation", etc. You know you can make your own presets, right? Just tap the 'action' button and then 'Save To Preset ...': you'll be prompted for a name, and if it's a new name it'll make a new preset. I should probably document that somewhere. In the new version you can see how many cents from Sa you are for each string tuner, so if you have a list of cent values for your desired tuning you can just dial them in.

If you come up with useful presets, please let me know - it would be good to be able to share them with other users.

When you say, "the wave that is used to generate the tones" - do you mean the drone, the pluck or the sympathetic resonance? The strings are physically modelled, not samples - but the excitation stimuli (pluck, drone) are samples. Yes it's possible to change them, but I'd rather keep the interface as simple and powerful as possible.

I hadn't thought of making the string plucks able to receive MIDI - I'll look into how easy that might be to add.

Many thanks

I wrote too soon before, because of how excited I was to use it. After another week of use, I have set up about 16 different presets that I am very happy about. I used this chart to get me there, http://www.sfu.ca/sonic-studio/handbook/Just_Tuning.html but have also set up a few more western modes as well.

There is some really magical stuff happening when turning down the mic mix, and listening to the resonances on their own. I totally understand how hard it must be to add another tone into the physical model, I have played a lot with the extremes of the long and the plucked alot.

I did encounter an issue where when drone was turned on, the output would decay slowly and then no audio would come through, and I would exit out of the app and start again. Other than that it's working quite well.

I am going to record some work soon, and I'll throw a soundcloud link up here for everyone.

Keep up the great work.

Cheers!

upd:

Updated: May 23, 2013
Improved 'sitar-like' jawari tone

LOL, that's funny. And now I even more want to look at your synthesis module. Pretty please! :3

I'm glad you like Samvada - thanks.

Unfortunately it's a bit hard to send you the core string synthesis patch as it contains a custom external (2nd order allpass filter) and currently relies on messages from Objective-C for much of its functionality. However, I can describe what it does. There are two tricks used that add a bit of jawari tone to the basic Karplus-Strong waveguide:

1. Feeding a (small!) amount of the output back into the delay length of the waveguide. This simulates the sitar's flat bridge, slightly changing the length of the string with each vibration. Watch out though, more than even a tiny amount will create the most horrible digital feedback sound ever.

2. String inharmonicity. Adding an allpass filter in the Karplus-Strong loop (I used a second order one) will do this. For some reason the combination of this with point 1 above results in something like the jawari sound (though it's not perfect).

You might want to check http://www.talaash.at/sitar/ which has a great sitar model. I had to cut a few corners in my version: cramming 13 oscillators into an iOS app is pushing things in terms of performance.

Let me know (here or on email) if you have any other questions.

What struck me as an interesting possibility with the second delay tap case is that it could be set to some different length. Of course this has no basis in reality, but it could be an interesting way to change the phase of the delay modulation, or possibly emphasize certain harmonics.

I'm also imagining that you could crudely model the bridge shape by inserting a nonlinearity between the delay read and the [vd~] delay time input, and maybe also insert a [lop~] or similar. I think this might help to avoid unbounded oscillations.

In general it seems that you can do lots of abstract and more or less arbitrary variations to basic physical models with the result not necessarily sounding obviously synthetic. I'm consistently surprised at how easy it is to make something sound plausibly acoustic, even if it doesn't necessarily suggest a specific instrument.

• different length delay modulating the string length. Yeah, I guess what you'll get there is like FM sidebands, except with both carrier and modulator resonating according to the input.

• nonlinearity in the return. Yes, I used that idea in Samvada - a cubic soft clip, I think.

• "acousticness" - absolutely. "Physical modelling" sounds impressive but it's really very simple elements. It's amazing how organic the results can be.

What this suggests to me is that maybe these effects could be crudely simulated by adding delay self-modulation (with the absolute value of the modulating signal) into a feedback delay network.

And I guess this could also incorporated into other configurations. I often use small FDNs with 3x3 rotation matrices to obtain various metallic and resonant effects. This makes me wonder what kinds of effects I could get this way, either for "instruments" with impulsive or noise-based input or resonators processing other sounds.

simply couldn't help it.
Thank you Iotic, you inspired me a lot (as all forum contibutors here).

So I tried to make a Samvada-inspired patch , and the topic is http://forum.pdpatchrepo.info/topic/8269/sympathetic-strings-resonator-inspired-by-samvada-app .

So fun when you learn things and get immediately rewarded with a simple yet functional patch

Suggestions welcome !

Nau