Few people have heard of it, yet many consider John Blankenbaker's KENBAK-1 to be the first commercial personal computer.
DIY: Build An Analog Synth With A Screwdriver
By bohus
The mad scientists from Gakken in Japan have done it again. This time they've created an easy to assemble kit to build your own battery-powered mini analog synth. You play it with an attached stylus much like the famous Stylophone of the 60's, 
but it has far more control over the sound. You can adjust the low frequency oscillator, the attack and sustain, and a few other parameters that shape the analog madness.
The kit doesn't require any soldering from what I can tell, though if I were building it I'd solder the connections just to be extra sure. Since this kit is part of Gakken's series of adult-oriented science kits, the documents include a short lesson on how synthesizers work, as well as a magazine with articles on the history of electronic music and interviews with noted artists.
Especially intriguing is that you can control the SX-150 using another of Gakken's kits – a mini Theremin! 
Their Theremin is bright red plastic and built to look like Theremin's original podium shaped instrument – as played by a 12” GI Joe. This demo video shows some Japanese electronic musicians controlling the SX-150's sound using a rather provocative looking microphone.
Though not officially available in the US, some poking around will find some Japanese dealers who will ship you a kit from Japan
Gakken sx-150 on Ebay
Gakken theremin kit
Add MIDI control to the SX-150 [HobbyMedia.it]
related:
Gakken super 8 projector kit
Build a tube amplifier
Record a record using a blank CD
