I have been conducting a series of music electronics workshops in conjunction with Switched On, the awesome Austin synthesizer shop. In the November 2011 workshop we build a new mini synthesizer that I designed.
It is a simple CMOS synth, but it has a lot of features:
The cardboard box enclosure is a bit of fun. One of the best parts of DIY synth is building the enclosure. I have seen, and built, all sorts of enclosures, but I think this might be the first synth built into the box that the parts come in.
I actually had eight kits leftover from the workshop, but they're all gone now. If you want to build one yourself, just follow the diagrams below. Given that the preceding sentence constitutes the complete build instructions, I would consider this at least an intermediate level project. Of course, if you do want to build one and have any questions, feel free to contact me. I am always happy to help. The below diagrams are also available in this PDF file, which also includes the bill of materials. Oh, and you can use any enclosure - it doesn't have to be cardboard!
Synth In a Box Sample Sounds by Delptronics