Hey Patrick,
It's the "everything in-between" bit that is hard. A hihat is one of those instruments that seems really simple, but on deeper analysis you see it is an amazingly complex and subtle device (which is obvious when you hear a really good drummer playing). With samples you can get the usual opening and closing strike sounds, and the cup/clash.
But if you want a really good model you probably need to look at physical modelling and granular methods.
The two parts can rattle against each other causing new excitations.
Sometimes the top cymbal rotates around the bottom one, creating a rolling 'clatter'.
The pressure of the pedal pushes them together harder increasing the frequencies (speeding up the roll - like if you push down in the middle of a rolling dinner plate) and damping both parts more.
You can hit it on the edge or at any radius from the centre. As a simple rule the spectral complexity increases as you move outwards, hitting the bell in the middle produces a purer, shorter tone.
You can use the tip of the stick, or brush, or hit lower down to get a less elastic impact with more energy transferrence (louder and noiser).
So for the input vector; for pedal you probably want two continuous ranges, position and pressure (where they are touching), and for excitation you probably want two more impact event parameters, energy (0.5 * mass * velocity^2) and duration (impulse).
You can also model leaving the stick connected, which damps the vibration at one point and reduces the modes.
A full physical model of two interacting centre supported circular plates is certainly too expensive. FM methods can give you the raw spectra to blend according to interaction rules. (In fact - because the relationship of spectra in both FM and the disc modeal model both derive from Bessel functions you can get very natural evolution if you choose the right synth model - complex FM with multiple modulator sources works extremely well.)
The trick is mapping the control params onto the synthesis params. As they come together you can tap off a little bit of the lowest and strongest vibrational mode (lop~ -> max~) and use it to make impulse spikes that amplitude modulate the other plate. Of course this is a reciprocal relationship (the lower plate also rattles against the upper one) - so it's ring modulation of the two maximum excusions to get a 'rattle modulator'. Moving the lop~ up and bringing the clip down will create the impression of the plates being forced together.
The other approach is to make a parametric map from samples into a great big wavetable to use as grains. I have never tried it but I think that would work well for hi-hat.
a.
On Wed, 26 Nov 2008 01:27:23 -0500 patrick puredata@11h11.com wrote:
hi,
would it be possible to patch an acoustic hi-hat pedal complete with heel-splash sound, closed sound, open sound, and everything in-between.
i am not so sure where to start, i want a sampler-base solution.
adsr, playing with filters, morphing of sounds, using 2 samples or more (open, middle, close, very close). i would gladly pay a beer for this.
pat
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