There has been some discussion on AH on the Alesis ION filter types. It's interesting that they are not listed in detail on the Alesis site. I thought I'd put up a post with the list so far. Title link takes you to a Sound on Sound review of the ION where the majority of the below came from. However, some new filters also listed below, were added since the SOS reveiw. Here's
a link to the details on the OS updates to date.
'mg': a four-pole low-pass modelled on that of the most famous monophonic analogue synth ever made.
'ob': a two-pole low-pass closely resembling the one in a classic synth xpander... whoops, I mean expander module.
'ob': a two-pole band-pass.
'ob': a two-pole high-pass.
'rp': a four-pole low-pass modelled on the one in a popular semi-modular synth.
'tb': a three-pole low-pass (think 'little silver bass synth').
'jp': a four-pole low-pass (from an eight-voice synth noted for its coloured buttons amongst other things);
'Eight-pole low-pass': all the filters from here on were created for the Ion; this one gives a very steep cutoff.
'8ve dual band-pass': two two-pole band-pass filters spaced one octave apart.
'six-pole band-pass': like an exaggerated version of the 'ob' band-pass.
'phase warp': an analogue phaser effect based on eight all-pass filters in series.
'comb filter 1': multiple resonant peaks and notches which are not harmonically related.
'comb filter 2': as above, but the signal is additionally filtered to warm up the sound.
'vocal formant 1': three band-pass filters emulating 'ah' and 'oo' vowel sounds.
'vocal formant 2': as above, but 'oh' and 'ee' vowel sounds.
'vocal formant 3': a five-band formant filter.
'band limit': a two-pole high-pass filter and a two-pole low-pass filter in series, limiting the signal to everything between them; resonance adjusts bandwidth.
New Types:
'OP 4-Pole Highpass - This filter is based on our "MG" 4-pole lowpass filter model. It has a steeper cut-off and more extreme resonance than the "OB" highpass. Like the "MG", it will self-oscillate when the resonance is turned all the way up. It can thus be used as a fourth (or fifth) oscillator.
'Comb 3 - Based on a different design than Comb's 1 and 2, it has deeper notches and more pronounced resonance.
'Comb 4 - Similar to Comb3, but with negative feedback. This will oscillate and even clip when the resonance is turned up.
Title link takes you to Seth Elgart's website. I recently posted Jim Aikin's thoughts on Melody Over Texture. This came from a thread on SynthSights on the topic of the musician and the synthesist and the topic of sound and texture driving a piece of music vs. the musician driving the melody and composition. Seth put up a couple of examples of Music vs. Sound. In one track, Fifty Five, he gets lost in textures from the Waldorf Q, he states that Q drives the composition itself (BTW, this is a good demo of the Waldorf Q 's swirly textures). He states, "It more or less wrote itself. I didn't have much to do with it really. I just played it." In another track, Celebrate Life, Seth critically composes and drives the music. It's interesting when you think about how you create music. I lean more towards the sound leading me - it seems more like an interaction between me and the synth. Two things immidiately come to mind when I think about this, one, Bob Moog's magical description of how you feel sound and the instrument - how you connect to it in an almost metaphysical way; and two, this video of Jean Michel Jarre where he talks about leaving room for the music to drive itself. How do you play?
Title link takes you to Tim Wade's blog on the ORT Synthesizer. Thanks Tim! 
Another via Mattias. It's a wall of oscilloscopes. Title link takes you to a bigger shot. Also make sure to check out Mattias' site.
Title link takes you to the SynthModules site. The PSIM-1 is currently sold out. Details on the PSIM-1: "The heart of this module is a powerful miniature computer (microcontroller) that processes 100,000 instructions per second. It is programmed with your Windows based PC in a simple and easy to learn form of BASIC. Each of the four analog outputs can be programmed to output 1V/Octave CV-OUT as a pattern sequencer and complex event generator, or simply as a gate. This is just the beginning. Use any of its four analog outputs as a programmable LFO to gate your ADSR and set up extremely complex filter sweeps. Clock your Binary Zone with complex events. Imagine what you can do with your filters! Generate CV along with extremely complex sequences that are only limited by your imagination. Unlike most typical analog sequencers, you can change the timing of the spaces between notes and/or gates. Like I said, this is all just the beginning. Additional add-on modules will follow. Unlike a one-time programmable ROM, you can change the program anytime you wish by simply plugging in a cable and downloading the changes to your module. The program remains in memory even with the power off until the next time you want to change the program. Once programmed, you can disconnect your computer and use it as you would any other module. Want random gate and CV sequences? Here you go! Change a few lines of code and you have chaos at it's finest! "
