During HRV computation, all extracted parameters are stored in a new CSV file, with one row per time step. Building on the experiments conducted in the previous semester, a dedicated conversion script was developed to translate these HRV parameters into MIDI continuous controller (CC) signals for use in sound synthesis and composition.
The conversion process is based on three core principles. First, all physiological parameters are represented as independent CC lanes, allowing each metric to modulate a different sound parameter in a digital audio workstation. Heart rate is exported both as a raw value (clamped to the MIDI range 0–127) and as a normalized value scaled across the full CC range using global minimum and maximum values. This dual representation enables flexible artistic use of absolute and relative changes in heart rate.
Second, the script applies time compression to the physiological data. Because HRV parameters evolve slowly, real recording time is compressed so that long physiological processes can be perceived within a shorter musical timeframe. For example, several minutes of HRV data can be mapped onto a few seconds of MIDI time, while maintaining the temporal relationships between parameters. The compression factor can be adjusted depending on the desired level of temporal abstraction.
Third, normalization is performed using global minimum and maximum values computed across all available HRV CSV files. This ensures consistent scaling between different recording sessions and prevents abrupt changes in mapping behavior when multiple datasets are combined within the same composition.
For each time step in the HRV CSV file, the script generates a group of MIDI CC messages that occur simultaneously. Each HRV parameter is linearly mapped to the MIDI range of 0–127 and written as a CC event at a fixed musical tempo. The resulting MIDI files therefore encode physiological dynamics as continuous control data, independent of note events.
This approach produces MIDI files that are immediately usable in digital audio workstations such as Ableton Live. HRV-derived CC lanes can be assigned to synthesis, filtering, spatialization, or effect parameters, forming a direct bridge between physiological analysis and sound-based artistic exploration.
