Revisiting the PSS-790

Yesterday I spent some time tackling the mess in my attic, and classically uncovered a bunch of really useful bits underneath the debris. Somewhere amongst them was a trusty old companion, a PSS-790 that I modified in 2011/2012 and used extensively in my Ginko project:

PSS790 - 3.jpg

The PSS-790 is a fairly straightforward amateur keyboard, it has mini keys with no velocity, 99 presets of Yamaha’s “Advanced Wave Modulation” sounds and rhythms, a basic song editor, assignable percussion pads and the Vector joystick – for a keyboard that is almost a toy, it has some pretty ok features. The sounds are clean, some of them are interesting (like the theramin like 68 “Chorus” sound and 74 “Synth Strings” – yes I know them by number!!), the vector joystick allows for layering of sounds at the expense of polyphony and in a similar manner, there is a “Harmony” setting that has various instant chords and strum effects, but doubles up the voices used.

But the best thing about this keyboard is that it utilises Yamaha’s AWM technology – I discovered some years ago that devices that use the original AWM system will always make very good candidates for modification! This was actually the second PSS-790 I modded. For the first I used similar points, but limited myself to 8 switches in total – for the second I went all out with a 30 point patch matrix, breaking out all the pins of the AWM processor as well as unlocking some other interesting points. By patching something on the matrix, you effectively create a short circuit across the sound brain of the keyboard and all kinds of exotic results follow.

PSS790 - 2.jpg

My original mods

As well as the brain scrambling patch matrix, I included a patch socket that seems to guarantee drone effects of some flavour (different for every point on the matrix and sound loaded on the keyboard) and another socket that results in automatic aleatoric chaos! It’s hard to tell what the drone patch actually does, it seems to make notes hang with envelopes open, or it could be scrambling the synths reverb – polyphony plays a part in the results you hear, so the reverb is probably just some hacky voice envelope behaviour as opposed to an actual processed effect.

The AWM approach is to use very short samples of real world instruments, and then combine them by layering, re-pitching and amplitude enveloping to produce the variety of sounds on the devices using the technology, it’s effectively a very basic form of granular synthesis – I think that what makes these instruments interesting to modify is all of the described functions of AWM are handled by a single or pair of large custom chips. So when you cross the nerve endings of the instrument, you can get pretty spectacular results like obscure enveloping, samples playing in reverse or choppy patterns and odd sample layering combinations. The PSS-790 isn’t the craziest of the AWM instruments I have modified (I think the PSS-31 has to hold that title) but I think it is by far the most musical results I have achieved from a bend project PERIOD. At least I think so – my definition of music may be quite squiff compared to yours!

There are a number of things that work really well with the modified PSS-790, one of them being that the standard controls across the keyboard tend to work as normal in combination with the mods – so for example it is very easy to get melodic drones going with simple patches, once you have them you can often use the pitch, vector and harmony controls to manipulate them. Another thing that sets this system apart from many others is that it behaves very predictably, if you load a sound and patch something in, you will always get the same results (with the exception of the chaos patch!!).

The downside here is that you have 99 sounds and a huge amount of possible combinations in the patch matrix, including multiple stacks on one socket – not everything sounds good and trying to remember what definitely does is like trying to memorise a piece of music in itself. Melodic layered drones, glitched squelch and heavy distortion are all very possible with slight changes to patch and settings – playing live with this keyboard was always a real challenge!! However – for its capability to produce mesmerising sounds and an endless serving of surprises, I will always have a soft spot for this instrument!

I will try and find the time to fluff this article out with some samples soon

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