259e Sequence IV [Buchla Does Bossanova]

Published on Oct 8, 2012 by boobtube356

"Reconstruction of the second vid in this series. There were a few changes, but the result is close enough and simpler.

The key here is sending an irregular pulse to the 266e QRV section. The result selects stages in the 250e running in continuous mode. The irregular clock comes from a steady pulse to the 281e, with the decay amount determined by a 266e FRV. The trick is to use the envelope as the clock output instead of the pulse. This means the clock will always be on a regular time, but it may skip a few input pulses if the decay is still in progress due to a long decay time. By adjusting the decay fluctuation rate and decay offset, you have a lot of control over the density of the output. It can be mostly on, mostly off, or somewhere in between.

Another key here is to use the 255 as the envelope for the sound, based on the ALL output of the 250e. This means rapid changes will get emphasis. I found it best to use a very small nonzero rise setting on the 255 so that the levels would move around more gradually. However, this leads to a sloppy envelope. The fix is to use a 281e for the envelope instead, and use the 255 to control the level of it using the VCA in the 256e (or 254v). This gives you crisp envelopes with variable emphasis. Best of both.

Another key here (possibly too much in this vid) is the exploitation of the stage jitter in the 250e. In continuous mode, it is possible that the input stage selection voltage will land very close to the center between two stages. When this happens, the 250e toggles back and forth between the two stages. The rate of the toggle is usually fast, but sometimes it's a little slower. I found that the number of steps selected in the 266e QRV section affects the likelihood of the effect. It seems to happen at a setting of 7 or 13. A side trick here is to apply a small amount of slew to the stage selection voltage using the 255. This causes the 250e to issue two successive pulses, almost too quickly to hear, and only sometimes (depending on how far away the successive stages are), which causes the envelope in the 255 to boost more. It adds more variation to the emphasis on the 281e.

The trumpet sounds from my earlier vid in this series was confirmed to be the 259e, tracking mode, modulating the morph, hard sync, mem skew b at about 2 o'clock, just like I had claimed. I hit them here too, but decided to do something a little different this time instead, hitting something closer to the old buchlajazz version of this on my soundcloud channel.

I think this patch would benefit from a retuning, and maybe more tweaking, but the main aim was reconstruction and documentation. Some of the techniques here are broadly applicable."