Voder

The Voder was the first machine that could talk, demonstrated at the 1939 New York World's Fair and invented by Homer Dudley at Bell Labs. It had no vocabulary and no text input: it made two raw sounds, a buzz and a hiss, and a trained operator shaped them into speech in real time using ten finger keys, a wrist bar and a foot pedal. Operators trained for months.<br><br>

This card is that instrument with eight bandpass filters instead of ten, played from its own panel or from a Music Thing 8mu over USB MIDI Host. It is not a vocoder and not a text-to-speech engine - nothing analyses an input signal and nothing knows what a word is. What comes out is whatever your hands put in.<br><br>

Turning the card on gives BABBLE, where each knob drives several things at once so it talks from a single gate with nothing else attached. Main sweeps the vowel and the pitch together, X sets how fast and bright the syllables are, and Y runs from a rounded hum to a breathy whisper. Switch up for a second page that shapes the voice itself rather than what it is saying: size, animation and consonants. The momentary switch is a gate - hold it and the card sounds for as long as you hold it, with nothing patched at all. Hold it for two seconds and it starts talking by itself in phrases, with pauses long enough to read as breaths.<br><br>

Holding the switch down at power-on gives the deliberate mode instead, one knob to one parameter, where the vowel is a point in a three-dimensional space: how open the mouth is, whether the tongue is forward or back, and how far the lips are rounded. Every vowel lives somewhere in that cube, with diphthongs on the way between.<br><br>

With an 8mu the two vowel axes are on faders 1 and 8, the outermost pair, so the hand spans the device; rounding is the left-right lift of the controller. Fader 3 is breath, fader 4 pitch, fader 5 brightness, fader 7 volume, and faders 2 and 6 shape the plosive. Tilting front to back swings the volume either side of the fader, so a phrase can be swelled and ducked without letting go of anything.<br><br>

Every CV input adds to its control rather than replacing it, so a random voltage wanders the sound around wherever the knobs are parked and nothing goes dead when a cable goes in. CV In 2 sweeps the vowel cube diagonally, which is the input to patch a sample-and-hold into. Audio In 1 sums with the internal sources rather than replacing them, so the card can speak over whatever is patched in, both shaped by the same vowel.<br><br>

Technical: eight 2-pole IIR bandpass sections at 250, 450, 700, 1000, 1400, 1900, 2600 and 3800 Hz, Q=4, entirely fixed point with Q15 coefficients. The buzz is a polyBLEP-corrected sawtooth. Core 0 runs the 48 kHz audio interrupt at 192 MHz; Core 1 owns the TinyUSB host stack and nothing else, and never parses inside a USB callback. All code is copied to RAM to keep flash-cache jitter out of the audio path. The whole engine is 32-bit integer arithmetic - measured at 60% of the per-sample budget on hardware, where the 64-bit version it replaced was at 100%.

Copy the UF2 onto the Computer's program card (RP2040 bootloader drive).