Ensemble : Bluetooth MIDI performance device

I created a device that uses the accelerometer of the M5StickC PLUS2 to perform music on a Bluetooth MIDI-connected instrument. While fine control is difficult with tilt-based input, it is easy to produce interesting performances by switching between different types of chords and altering the sound quality.

Performance

A silver ball is displayed on the screen, and it behaves as if influenced by gravity, like a ball inside a bowl. It is pulled toward the center in the left-right direction, and from the back toward the front in the forward-backward direction. Therefore, the ball initially rests at the center front, but by tilting the M5StickC PLUS2, you can roll the ball in various directions. MIDI data corresponding to the ball's position is then transmitted via Bluetooth.

Hardware

Only the M5StickC PLUS2 is used, but since it only sends MIDI data and cannot produce sound on its own, a separate device capable of receiving MIDI over Bluetooth is required.

For example, GarageBand running on iOS can receive MIDI over Bluetooth and play sounds such as piano or guitar.

Chord Structure

EnsembleThe ball on the screen simulates a bowl-like curved surface. It is pulled toward the center in the left-right direction and toward the frontmost area in the forward-backward direction. By tilting the M5StickC PLUS2, the ball rolls across the screen, and its position changes the timbre and pitch.

The screen is virtually divided into a 3 (left-right) × 8 (forward-backward) grid.

• The frontmost area is silent
• The second row plays only the key note
• As the ball moves further back, the chord expands with higher and lower tones
• In the backmost row, a 7-note chord is played, evenly distributed across four octaves

Conceptually, a line is drawn connecting the central point in the second row with a point representing 7 notes evenly spaced over 4 octaves in the backmost row. Each row plays chords approximating the line passing through those points.

The left-right direction changes the key pitch:

• The right area plays a chord a perfect fifth above
• The left area plays a chord a perfect fifth below

If you tilt the M5StickC PLUS2 significantly to the right, the pitch range of each area shifts leftward, and the rightmost area adds a chord a fifth above the previous top pitch.

At startup, the center area is set to C major. Pressing the button at the bottom of the screen toggles between major and minor, switching to C minor.