Every sound is synthesized live with the Web Audio API; there are no samples. Each active alert drives one oscillator note, with pitch and timing both quantized so the alert stream comes out as music instead of beeps.
Pitch is snapped to a five-note scale built from a 55 Hz root, where each degree is a set number of semitones above it: frequency = 55 × 2^(semitones / 12). Severity sets the octave, waveform, gain, and duration of the note. Each resource is hashed to a fixed scale degree, so it always sounds the same pitch. The number of active alerts sets how many notes play per bar, and all of it is locked to a 16-step beat grid over a bass, pad, and drum bed. ACK and SDT alerts are scaled down in gain.
What "quantized" means
It means snapped to a fixed grid of allowed values instead of landing anywhere. Two grids are in play.
PitchAn alert never plays an arbitrary frequency. It is snapped to a note in the active scale, the handful of semitone steps above the 55 Hz root, so out-of-key pitches cannot happen and any combination of alerts stays in tune.
TimeA note does not fire the instant its alert is processed. It is snapped to the nearest slot on a 16-step-per-bar beat grid, so notes land on the beat instead of scattering. That is the difference between rhythm and random clicks.
Same idea a drum machine uses when it snaps your notes to the grid: take a continuous value and round it to the nearest point on a defined grid. Open Reference for every value, or Settings to change them.
Glossary
SemitoneThe smallest step in Western tuning, one twelfth of an octave. Each semitone multiplies frequency by 2^(1/12).
OctaveA doubling of frequency. The same note an octave up sounds twice as high, and spans 12 semitones.
RootThe base pitch the scale is built from. Here it is 55 Hz, the note A1.
Scale degreeA numbered slot in the scale. Degree 0 is the root, and this build uses five of them.
PentatonicA five-note scale. Its spacing is why almost any mix of its notes sounds consonant.
WaveformThe shape of the oscillator wave, which sets timbre. Sine is pure and soft, sawtooth bright and buzzy.
GainLoudness, the amplitude of a sound.
PanStereo position, anywhere from full left to full right.
BarA repeating group of beats. Here each bar is 16 steps.
BedThe backing under the melody: bass, pad, kick, and hat.
PadA soft, sustained chord that fills the space behind the notes.
MotifA short musical idea that recurs. Here, each resource's fixed note.
ReverbSynthesized space, the tail a sound leaves in a room.
LowpassA filter that removes highs. The Tone knob opens and closes it.