To get started with your own prog-rock sound effects, consider building this low-fi synthesiser. The construction is quite easy, and the results speak for themselves - for example in the following video:
With a little extra work this could be mounted neatly inside an enclosure and be useful for budding musicians, sound-effects fans or irritating people. Furthermore this kind of project shows that the Arduino world is more than just digital inputs and outputs - so to get started visit the project page here for the circuits and Arduino sketch. And we're on twitter, so follow us for news and product updates as well.