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Some fun synths examples,

Theo Verelst

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I made. Over the years I've made some interesting synthesizer designs, maybe some people find it fun to hear some of that.


First, there's the "string simulator" software, doing a complicated modeling of strings of a guitar, where motion is computed per little string segment, there's some feedback (like from the guitar amp) back to the strings (up to the point of almost resonance), and string mutually influence each other. I made this years ago, so with modern computer technology, more could be done to make this simulation more interesting and complicated, but here's an example I presented years ago in an Free and Open Source conference, I'm playing a 4 octave touch sensitive (cheap) midi keyboard, and recorded the sound output of the program straight (no additional effects or processing):




A little shorter ago I worked on mathematical synthesis, where I take a formal algebraic mathematical equation, and with high accuracy render it to a sound. So I could put a block on a graphical canvas, for instance a "sine" block, connect it with a virtual output, and compute a sound wave corresponding the that network, with very good formula conditioning and making high accuracy samples with 64 bit floating point computations. Here's 20 sine waves, each with a different envelope, and a little complicated Frequency Modulation:




Here's an example and some pointers to the combination of Open Source software packages I used and made for the purpose of creating sound formulas (based on a time parameter) from random networks of mathematical elements, and even creating a standalone (Linux or Windows) result program from that formula that allows polyphonic playing of the created waves over MIDI, as far as processor power allows: Creating arrays of wave formulas with BWise .


I've tried how the solution of a differential equation (you may remember them from high school) can be used to make waves and combine them with other mathematically created waves and some (Linux / Jack) plugins (in this case Hexter DX7 simulation, and a sound canvas (Qsynth) with drums). I got this rendering of Hasta Manana from an internet found MIDI file:




The formulas for the left panned solo sound and the right panned synth-like bass are (skip this if you're not mathematically interested):


[font:Courier New](

sin( 6.2831*110*x)*exp(- 2*x)

+(1/2)*sin(2*6.2831*110*x)*exp(- 4*x)

+(1/3)*sin(3*6.2831*110*x)*exp(- 6*x)

+(1/4)*sin(4*6.2831*110*x)*exp(- 8*x)






) / (




a complicated set of differently exponentially damped harmonics of a sawtooth wave, slowly becoming more sinusoidial (less overtones) ,


[font:Courier New]



The solution of a 2d order differential equation computed, in a form which can be listened to by scaling and time scaling and shifting the solution :



Now some hardware for sound synthesis I've worked on, this is a Xilinx Field Programmable Gate Array based electronics board (few hundred bucks), which contains a medium amount of freely programmable computer logic:


http://www.theover.org/Fpgasynth/01072008318bm.jpg (see here )


I've programmed a few analog-type of synth patches for a synthesizer design made by someone else (Scott Gravenhorst, I made some changes/bug fixes), like this one:




These boards, with the whole synthesize emulation start up to fully operational in (sub) second(s), take very little wattage, and are solid state (data is in flash rom). There are other designs for it too, like FM, harp simulation, etc.



Now a design I made completely myself (all the sources are available in the PD, free for non-commercial use), which also uses a programmable logic chip, in combination with a general purpose Digital Signal Processing board (with Analog Devices "Blackfin" chip and 24 bit AD and DA convertors), described on my server.


This was the first prototype, shown in combination with another DSP board, acting as reverberation/delay unit (not open source, it's the board with the "VU meters"):




Here's a (long) demo, played live on these boards (with self made midi interface, don't mind the noise coming from limitations of the setup, demo is straight recorded from audio out, no processing, midi sequencing or editing):




I've presented the demo at AES at the time:




and the resulting prototype (fully working, with enclosure, startup time under a second, parameter display, but no patch storage, additional analog chorus input input and preamp) was on a big dutch musical instrument conference:





Please keep in mind my server has limited upload bandwidth, you may have to first download the examples instead of playing them live.


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To finish my line of thinking about some of the essential options for synthesizer technology, this should be in the mail in the foreseeable future:




Dual ARM processor, capable programmable logic, 16-core special RISC chip with considerable connection bandwidth, Ethernet, USB flash card with Linux, quite some total processing power of various kinds.

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I at once get it and don't get it.


I think it's like building a multistory house for yourself out of lego. You have complete control over what you do, and at the end of the day, you have built something for yourself completely by yourself and can sit back and look with pride at the awesome thing you've built.


Or..., you can pay a contractor with much more experience and better tools than you to build you a brick house that will look a lot nicer and probably be of greater utility to you in the long run.


Deriving your own synths from mathematical models is cool (if that's your thing) and I'm sure it leaves you with a sense of satisfaction when it's done, but for the sake of making music, why not stick with professionally modeled instruments (eg, AAS LoungLizard which is purely modeled) or - gasp - sample-based instruments, which sound a whole lot nicer?



Nord Stage 2 Compact, Yamaha MODX8

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Some people want to focus on results. They will keep an old instrument for years and use it to master the music.


Some derive pleasure in playing with new toys, and others derive pleasure from creating new instruments.


Most of us are a mix of these things, and have to choose how to balance our time pursuing them.


I'm glad there are guys like Theo and Guido around, as innovation these days seems to be coming from people like them, not the major instrument companies.


It's all good.



"I keep wanting to like it's sound, but every demo seems to demonstrate that it has the earth-shaking punch and peerless sonics of the Roland Gaia. " - Tusker


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