this was answered in the thread i posted it from (corrections):

Step 10 sounded strange with that huge decay and when I heard the sample it was clear... 808 kick doesen't have that kind of a thud in the begining, that longish pitch-modulated thud is more of a 909 thing. 808 had a very short thud at the begining. You could somehow emulate it by having decay very little (depending on synth off course) in your 10th step and some hold (if provided i.e. if you have AHDSR envelope) in a way that it efectively creates just one or two cycles of higher pitched sines, and then settles down to about a G3. Another important part of 808 sound is that it starts with wave at full positive (Pi/2 cycle) rather than at zero crossing.

As for 909, you'll need a synth with triangle wave, filter and AD envelope for pitch modulation. Here you can have a longer pitch decay and a short pitch attack, and you need to saturate prior to filter, and then filter out the triangle but you need to take care that the filter is tuned to oscilator frequency at any point (this is how the sinewave is generated from a triangle in 909, they saturate the triangle into a hexagonal wave, then filter out into a sine). 909 also had a short burst of filtered noise for the initial click.

For both sounds pitch envelope needs to go quite a bit.

It's much easier doing it in an audio editor as J swift suggested. You could also create a long sample of overloaded and then filtered triangle wave for some authentic roland dirt, rather than clean deep sinewave, and then mess with that. Tuning at G3 (or G2 depending on synth) is pretty close to the default 808 tuning. As for 909 you need to experiment since you could tune 909 to many frequencies. Tuned about E3 it's close to default 909 tuning.

Anyway, here are some of my examples, FXP programs for Synth 1 and tuned samples made in audio editor (Audition in my case). FXP Synth 1 examples are closest in sound to originals on G2 (808) and E3 (909), on Fruity if you put the amp sustain all the way down. Other hosts may be octave lower or higher, not sure. Audio editor chops were done at 55Hz (A1) because it's the easiest tuned frequency to remember.

I created the original sine by making a 55Hz triangle, squasing it at about 6dB into the wave, and then applying a 4th order Butterworth Lowpass at 60Hz. It came out almost a clean sine. Nice for 808 but for 909 you may want to set the cutoff higher and try a 2nd order filter.

synth1 presets (you prolly need to register @dogsonacid.com):

http://www.dogsonacid.com/attachment...postid=4349499