Instruments

RMT Compose includes several built-in instruments for playback.

Available Instruments

Synth Instruments

Generated in real-time using oscillators:

Instrument	Waveform	Character
sine-wave	Sine	Pure, smooth, mellow
square-wave	Square	Hollow, clarinet-like
sawtooth-wave	Sawtooth	Bright, buzzy, string-like
triangle-wave	Triangle	Soft, flute-like
organ	Complex	Multi-harmonic organ
vibraphone	Complex	Bell-like, percussive decay

Sample Instruments

Using pre-recorded samples:

Instrument	Source	Character
piano	Sampled	Acoustic piano
violin	Sampled	Bowed string

Setting Instrument per Note

Using the Variable Widget

1. Select a note
2. Find the instrument dropdown
3. Select from the list

Using Expressions

In module JSON:

{
  "id": 1,
  "frequency": "...",
  "instrument": "sawtooth-wave"
}

Default Instrument

If no instrument is specified:

1. The note inherits from its dependencies
2. If no inheritance, defaults to sine-wave

Instrument Inheritance

Instruments are inherited through the frequency dependency chain:

1. If the note has an explicit instrument set, use that
2. Otherwise, follow the frequency expression to find the parent note
3. Recursively check the parent note's instrument
4. If no instrument is found in the chain, default to sine-wave

For example, if Note 2's frequency is [1].f * (3/2) and Note 1 has instrument "piano", Note 2 will inherit "piano" since it depends on Note 1's frequency.

Propagation on Delete

When using Delete and Keep Dependencies, the deleted note's instrument is automatically propagated to any dependent notes that don't have their own explicit instrument set.

Synth Instrument Details

Sine Wave

The simplest waveform - a pure tone with no harmonics.

Best for:

• Pure, clear tones
• Bass frequencies
• Testing pitch relationships

Square Wave

Odd harmonics only (1, 3, 5, 7...).

Best for:

• Clarinet-like tones
• Retro/chiptune sounds
• Bohlen-Pierce scale (odd harmonics)

Sawtooth Wave

All harmonics present (1, 2, 3, 4...).

Best for:

• Bright, rich sounds
• String-like tones
• Lead sounds

Triangle Wave

Odd harmonics, but softer than square.

Best for:

• Soft, mellow tones
• Flute-like sounds
• Gentle melodies

Organ

Custom waveform with multiple harmonics (fundamental, 3rd, 4th, 5th, 6th, 8th, 9th) creating a rich, sustained tone.

Best for:

• Full, rich chords
• Sustained passages
• Held tones

Vibraphone

Custom waveform with strong fundamental, 4th partial, and 10th partial, plus a quick attack and long decay envelope.

Best for:

• Mallet percussion simulation
• Bell-like tones
• Percussive accents

Sample Instrument Details

Sample instruments use a single audio sample that is pitch-shifted to play different frequencies.

Piano

Single sample (A4 = 440Hz) pitch-shifted for all notes.

Characteristics:

• Quick attack, natural decay envelope
• Works best near the sample's native pitch
• Higher/lower pitches may sound less realistic due to pitch shifting

Violin

Single sample (C5 = 523.25Hz) pitch-shifted for all notes.

Characteristics:

• Slower attack simulating bow contact
• Special envelope handling for short notes vs sustained notes
• Subtle swell on longer notes (>0.5s)

Mixing Instruments

Different notes can use different instruments:

{
  "notes": [
    { "id": 1, "instrument": "piano", ... },
    { "id": 2, "instrument": "violin", ... },
    { "id": 3, "instrument": "sine-wave", ... }
  ]
}

This enables:

• Ensemble arrangements
• Contrasting timbres
• Highlighting specific voices

Tips

1. Start with sine - It's the clearest for hearing pitch relationships
2. Use square for BP - Odd harmonics match Bohlen-Pierce well
3. Mix for interest - Combine different instruments in a composition
4. Match character - Choose instruments that fit your musical intent
5. Test with playback - Hear how different instruments sound in context

Future Instruments

Planned additions:

• More sample instruments
• Custom sample loading
• FM synthesis
• Audio effects (reverb, delay)