Now you can make your own custom version of one of the most iconic musical toys of the 80s.
Perhaps the most iconic 80s music toy was the Magical Musical Thing from Mattel. The TV commercial featured a kid playing melodies with one finger on the toy’s keypad strip — and finishing by playing it with his head! It featured a sound circuit that was designed around the cheapest and most basic building block of digital electronics: the 4049 CMOS hex inverter chip.
Usually used for decoders and multiplexers, the lowly 4049 was re-imagined by Mattel’s thrifty engineers to create musical tones. Three of the IC’s six logic gates were linked head-to-tail with a resistor and capacitor to create a simple, self-oscillating on-off/on-off square wave generator. The output of this oscillator was hooked up to the remaining three inverters in parallel. Their combined outputs were just enough to directly drive a speaker, with no audio amplifier needed!
A network of resistors created the various musical tones. This was done using a cleverly designed membrane switch pad. The top and bottom layers were made from a single, folded piece of Mylar, printed with conductive silver traces connecting strips of resistive paint. The middle layer was a die-cut insulated spacer with holes positioned to make touch points, each labeled for a different color-coded musical note. Touching the membrane pressed together two conductive strips, which completed the circuit through a path of resistors, producing a single musical tone. The shorter the path, the less electrical resistance, the faster the circuit oscillates, and the higher the pitch! Beep boop! Follow the color-coded notes to play a song or slide the “Thing” over your body for a flourish of notes.
Now you can make your own custom version of this classic 80s toy. Wire up the circuit, paint a membrane keyboard, and make a housing (or put it in some repurposed container). This DIY re-do has a new added feature: a circuit-bending touch point.