Envelope filters and user interface design

So I've managed to find time to get back to playing around with some new ideas...

One thing that has always interested me is the how users interact with devices. As with any musical instrument, the interface, as well as the sound-production method, determines the nature of the sound you can get out of it. Obviously, with a six-string guitar, you can play a maximum of six notes at a time. Not so obviously (to non-musicians), the tuning of the guitar limits the chord voicings you can play, part of the reason people experiment with different tunings. Electronic instruments can abstract the sound-creation potential away from the interface, making them very powerful but at the same time sometimes very frustrating to use. If you've ever programmed a DX-7 you'll know what I mean. At the same time this abstraction allowed the DX-7, for example, to be created and made available to people to utilise. Perhaps in this case the end justified the means?

With effects pedals it's easy to make every parameter or variable available as an external control - I've done it myself. Sometimes this can be cool, however recently I'd been thinking I wanted to work on something simple. Something that put a new interface over a standard circuit / device (which pretty much all effects are these days already). Envelope filters have always been a favourite of mine - they appeal to me because you can interact with them without touching a knob, just using the dynamics of your instrument. There's little point in doing another version of the Mutron III or the 'new' 'envelope-filter-to-clone', the Lovetone Meatball and - besides - as a bass player I've always wanted some of the original signal blended in with the filtered signal, not to mention a simpler interface (even at the expense of flexibility). The range of controls on many envelope filters lets users create lots of settings that don't provide useful sounds (and here I'm admitting a narrow-minded focus on using the effect for funk / jamming / rock music, not experimental music). So I came up with following design goals:

• an envelope filter with an interface that 'restricts' users to 'useful' sounds
• an envelope filter that has a 'useful' blend of the original signal along with the processed signal
• an envelope filter - in one vain attempt at any originality! :^) - that sounds a bit 'different' to some / most others
• an envelope filter that is small (marketing decision - visually this would further set apart this device from the hulking Mutron IIIs / Meatballs and clones)

Utilising an all-pass filter, as used in analog phase-shifters, addresses points 2 and 3 above. Reducing the number of external controls to two takes care of point 1 and helps with point 4.

So this gives me a starting point for my design, which is important. Otherwise the multitude of possibilities overwhelms and distracts me, and I end up with lots of ideas and nothing built. Ideas are worth practically nothing until you've brought them to life in the real world. So lets see where this goes...