[sdiy] DSP 808 new demo

[Richie Burnett]

Hi Adam,

> As a TR808 owner for over 20 years, I was a little embarassed to only 
> discover recently the source of the Egyptian Lover "zap" sound - you 
> simply take the 14 volt trigger output from the "Accent Out" and plug  it 
> in to your mixer (making sure you turn down the trim!) Doh! And I  always 
> thought it was a high Q filter sweep!
> Brilliant - instant 80s electro. Hit me up if you want a sample....

My unit currently doesn't model this "gate pulse heard as audio" sound. It 
could easily be added as an alternative "zap" instrument if you think it's 
worthwhile though.  Please send a sample to my email, and I'll take a 
listen.

Many of those zap sounds in 80's electro music were made from a rapidly 
descending self-oscillating filter.  It's easy to dial up this patch on any 
analogue monosynth.  However, as you make the decay time driving the filter 
cutoff shorter and shorter, the frequency eventually sweeps down so fast 
that you can no longer perceive the sweep and it just sounds like a click. 
Engineers call these frequency sweeps "chirps" and they have similar broad 
flat frequency spectrums to impulses so it's not suprising that a trigger 
pulse and a very fast sinewave sweep sound similar.

> Anyway, Richie these sounds are alive. All you need now is a new take  on 
> the "16 LED runway" programming interface   ;-)

At present it only supports step entry.  You hold down an "Instrument 
Select" button and simultaneously tap one of the 16 keys to choose the 
instrument you want to edit the pattern for.  Then the LEDs above the 16 
keys illuminate to show the steps where that instrument will sound. 
Currently there is only on and off, but Paul Maddox managed to convince me 
to add 2 velocity options on each instrument track for a much more dynamic 
sound.  You can enter and exit step-edit mode while the sequencer plays, and 
it does the "night rider" thing with the dot running along the LEDs while 
playing in step-edit mode.

-Richie,