The Sound Gizmo is a very cool sound effects toy created in 1980 by Fundimensions, a division of CPG Products Corp (then owned by General Mills). This unit is rare and there is not a lot of information about it on the Internet. Dex of AEIOU has a short blog post about the Sound Gizmo, which links to an article about using a one on the Howard Stern Show, but other than a couple poor-quality YouTube videos there isn't much else beside chronicles of musicians using them in songs. Even though I have a childhood affinity for this device the general consensus is that it sounds like garbage! But could it sound better with... circuit bending? ;-P
I wanted to circut bend one of these for a long time so I bought one off eBay. The screwheads are tri-wing, so I also had to buy a bit (a #3 or #4 works). Once open I could see the internals were predictably basic. The Sound Gizmo uses what I believe was a common IC chip at the time: SN94281N. My pictures below show this specific chip is from Texas Instruments. I did a little research and found Dan Veeneman at Decode Systems has datasheet scans of a similar chip distrubuted by Archer. The author behind Achillies.com built a pretty cool enclosure for the demo cricuit (see also: this Reddit video).
My circuit bending goals, as always, were more practical than experimental. First, I wanted to add an output jack to run the Sound Gizmo through effects. The second objective was adding a switch to engage the CONSTANT and FADE buttons. This would free up both hands to work the PITCH/SPEED/VOLUME knobs simultaneously. Finally, I wanted to see if there were additional sounds I could squeeze out of the machine. It turns out I could, and I added some slight variations of a couple presets. Also, I added a contact point for manual pitch-bend/vibrato which makes the TONE preset more expressive. This bend turned out really well! Too bad I know almost nothing about electronics, there are lots of possibilities here.
JET PLANE | PHASER | EXPLOSION | GUNSHOT | TRAIN | TONE | MOTOR | SIREN | HELICOPTER
See also: Instruction booklet (PDF).