GateRunner

A browser-based MIDI step sequencer that generates MIDI files from binary-encoded note sequences using Forte number pitch-class sets.

Live app: https://ncg777.github.io/gaterunner/ (Until the GitHub repository is renamed, the app is also accessible at https://ncg777.github.io/gaterunner/)

Presets

GateRunner stores sequences as named presets in the browser.

• The selected preset loads into the working draft.
• Editing controls updates the working draft immediately for playback, MIDI export, and URL sharing.
• Use Save to update the selected preset.
• Use Save As to create a new preset from the current draft.
• Use New to create a fresh default preset.
• Existing single-preset local storage data is migrated automatically the first time the new preset system loads.

Import And Export

Preset files use JSON.

• Export Preset writes the current preset draft to a single-preset JSON file.
• Export Library writes the full preset library to a JSON file.
• Import JSON accepts either file type and adds imported presets without overwriting existing ones.
• If an imported preset name already exists, GateRunner keeps both presets by renaming the imported one.

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How Notes Are Computed in the Encoding Scheme

This application uses a binary-based encoding system to determine which notes are played from numerical values. Here's how it works:

1. Binary Representation of Numbers:

   • Each number is converted into binary, with bit 0 at position 0, bit 1 at position 1, and so on. For example:
     • The number 5 becomes 1010.
     • The number 10 becomes 0101.

2. Pitch Class Assignment:

   • Each binary digit corresponds to a position in the selected pitch class set going up octavewise to the maximal midi pitch. For example, for 7-35.11:
     • Position 0 = C
     • Position 1 = D
     • Position 2 = E
     • Position 3 = F
     • Position 4 = G
     • Position 5 = A
     • Position 6 = B
     • Position 7 = C
     • ...

3. Chords:

   • If multiple 1s are present, the corresponding notes form a chord.
     • Example: The number 7 (111) maps to C, D, and E.

Summary

To compute notes:

• Convert the number to binary (bit 0 = position 0).
• Map 1s to their pitch classes.
• Apply an octave offset for final pitches.
• Combine active notes into a chord.