Kick Drum Synthesis TR-808 style

K….

As you know I been thinking about kick drums:

If you don’t want a sample based kick there are a couple of common methods for synthesising them:

  1. use an oscillator – usually sine or triangle – as your start point with an amplitude envelope to control the decay length
  2. use a resonant bandpass filter triggered by an envelope and use the resonance to control decay length

both have their merits but i have to say i lean towards the latter

basically because i adore the depth of early Roland kick drums and the TR-808 in particular

so, how does it work?

i will try to show:

I’ve used the bang object to represent whatever MIDI/audio trigger you might want to use

The 1. in the message box triggers the adsr~ object – it will not work with just a bang as it requires a note on message

Decay is set to 4 ms with no sustain or release

the adsr~ object behaves as a trigger impulse for the filter – an equivalent of the TR-808 trigger logic although that is a more complex shape

The reson~ is a simple bandpass filter with gain set at 80, centre frequently at 50Hz and Q to 100 and the filter Q controls the decay of the kick drum

There are loads of descriptions of the TR-808 kick drum on the internet so if you are really keen i’ll let you search

What i will say, though, is that the TR-808 kick is not just a trigger followed by a resonance. There is a @3-6ms frequency sweep from somewhere above 100Hz to 50Hz on initial trigger which gives the kick some attack:

I have used the curve~ object to generate this

Note – I have used a message box to give the curve~ object its arguments:

initial frequency = 200Hz

final frequency = 50Hz

time = 5ms

Of course this only sets a basic emulation state and the curve~ object can be manipulated to generate non-linear curves usw…

 

All we need now is a decay control:

The number box at right is connected to reson~ right hand inlet which controls Q

As the output level of the filter decreases with increased Q i have kludged some control over the gain using the -20 into reson~ gain input – is quite close

 

 

 

 

So, there you have it, a basic filter based kick drum… I wonder how what I building is going…..

Looking forward….

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