hi

On Sat, 2008-04-05 at 18:56 +0200, raul diaz wrote:

Hi list!

I would like to open a thread about drum synthesis

I'm trying to make a tr909 emulator with an interface made with processing communicated with pd via OSC. I would like to make drum synthesis on pd based on chapters from fabulous sound-on-sound "synth secrets".

i once tried to emulate the 808 drumset in pd. however, due some stupid copy-some-stuff-around-in-order-to-backup-mistake i lost most of the instrumentes (basically only kick and clap are left).

a few words on the methods i used in order to model them:

• i downloaded a set of samples which different settings for each

instrument: http://www.smd-records.com/Websites/TR-808/page/samples.htm

• for sounds that consist of of several parts (e.g. snare: noise part

and two-oscillator part), i tried to isolate all the parts by subtraction (e.g. subtract the snare sample with 0 'snappy' from the sample with full 'snappy')

• i tried to figure out what kind of waveforms are used.

• i tried ot figure out what kind of envelopes were used. those are

probably the easiest part, because you can measure the times by looking at the signal graph (you don't necessarily need to hear them).

• i tried to figure out what kind of filters were used (e.g for the

snappy part in the snare). i found frequency analysis to be helpful in order to guess the correct filtertype (order, low/hi/bandpass, etc.)

i didn't have a very close look at the 909 drums, but i could imagine that those are more difficult to remodel. the diagrams are at least far more complex than the ones of the 808, as far as i can see it.

I'm not an expert on drum synthesis, so I'm making this work in order to learn about that. I know there is really expert sound designers on this community and I would thank a lot their help. Now, I'm trying to emulate a bass drum. I've take this scheme as example: http://www.soundonsound.com/sos/Feb02/images/fig13tr909bd.l.gif But I don't know how important for the final sound is the block VCO (sawtooth wave) + Waveshaping, instead of a simple sine oscillator. In synth secrets articles says:

"The output from the oscillator then passes through a waveshaper. This removes almost all the overtones, transforming the sawtooth into something very close to a sine wave."

the best would be to compare them. only the ears can tell, whether the difference is remarkable or not.

however, i think that the waveshaper part is critical. the interesting property of a waveshaper is, that the outcoming signal morphs its shape depending on the amplitude of the incoming signal. if i remember the kick of the 909 correctly, it sounds punchier at the beginning and gets softer while fading out, which is most probably the result of using the waveshaper. also when more than one oscillator is fed to the waveshaper, the outcoming signal is quite complex (though, this is not the case here, according to the diagram you posted).

Another doubt is how accent has influence on amplitude envelope attack and decay, what's the range of pitch sweep (from 400 to 40-80 Hz?) and its envelope decay value (200msg?).

yo. not that i am an expert, but i would assume, that the smaller the parts you're trying to remodel, the easier it will be. i think, that finally only the ears really can judge if it's done right.

And, finally I'm thinking about replaced noise generator + pulse generator with the trick used by roman haefeli on his 808bass (http://lists.puredata.info/pipermail/pd-list/2006-04/037663.html).

i remember, that i found a solution for the snare using simply noise and a filter. it turned out, that i could use one of the iemlib filters (cannot recall which, but it was sure a higher order one). the result sounded quite similar to the original, though the scope didn't look that similar.

roman

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