Linus Åkesson's Commodordion Is an Accordion with a Commodore 64 Twist

The humble accordion

Although rarely seen nowadays, the accordion was extremely popular in Europe throughout the nineteenth century, owing to it being invented in Germany. The instrument almost always features two independent keyboards that are each held by a single hand, and they can be moved closer or further apart thanks to the bellows joining the sides. Pushing and pulling the accordion forces air through the instrument where it can then be modified by the keys, thus creating different notes.

Linus Åkesson was inspired by the accordion and its often vintage nature, so it was only natural to combine it with another piece of retro technology, the Commodore 64. The resulting project, called the Commodordion, swaps the traditional piano-style keyboards for entire Commodore 64s while still having bellows between them.

Creating melodies and chords

Some of Åkesson's previous work has included his custom software named Qwertuoso. It is a small program made for the Commodore 64 that allows the keyboard to transform into a synthesizer. Along with keys for playing notes, users can press modifiers to select various modes, adjust the waveform, and perform special functions. Åkesson loaded Qwertuoso onto the left C64 for regular playing.

Programming simple loops

Unlike the left C64, the right one is a bit special in that it not only supports playing chords via the multiple rows of alphabetical keys in live mode, but can also store and play loops. To program a loop, the record key is pressed, which transforms some keys into drums, bass, or special chords. From here, the player inputs their sounds in rhythm with a background metronome and finally saves the result. Hitting either F1, F3, F5, or F7 during live mode will start playing the saved loop.

Bellow design

Due to the lack of need for moving air through a series of internal pipes, Åkesson had to figure out a different way of turning the force from the moving air inside of the bellows into changes in sound. His initial approach involved attaching a temperature sensor to a heating element and measuring how much the temperature changed in response to the flow of air around it. Unfortunately, this system turned out to respond far too slowly to changes in airflow and was even potentially dangerous.

Instead, Åkesson realized some time later that blowing into a microphone would produce very noticeable changes in its outputted waveform, thus making him realize that a simple microphone next to a hole in the otherwise airtight bellows could measure these pressure changes. The bellows themselves were fashioned by taping together old floppy discs (of course) with gaffer tape.

Outputting audio

The audio coming from each Commodore 64 is mixed equally within a mixer and is sent to a multiplying digital-to-analog converter (DAC). Since the bellows are supposed to control the volume, the waveform from the microphone is first converted into a series of peak levels thanks to an "envelope follower" program running on a microcontroller. This value acts as a gain on the C64 values in order to increase or decrease their total volume.

Playing the Commodordion

As seen and heard in his demonstration video, Åkesson' Commodordion is an amazingly capable instrument that can output a wide range of sounds with a fun 8-bit twist. You can watch his rendition of Scott Joplin's famous "Maple Leaf Rag" here on YouTube.