SoundFonts¶

SoundFont files (.sf2) contain audio samples and synthesis parameters used to reproduce musical instruments. Software and hardware that follow the SoundFont specification can render the same SoundFont in a consistent and portable way.

Terminology¶

Common SoundFont terms used throughout the documentation:

Preset

A single playable instrument defined by the soundfont.

Bank

A collection of up to 128 presets. Banks are numbered from 0–16383.

Program

The index of a preset within a bank (0–127).

Generator

A synthesis parameter controlling how samples are played (e.g. filter cutoff, envelope times).

Modulator

A rule that connects MIDI messages to generators.

Selecting presets¶

In a bank file, an integer key at the root or patch level selects the preset assigned to that MIDI channel.

Presets are specified using the format:

<soundfont file>:<bank>:<program>

For example:

1: piano.sf2:0:0

Channel assignments at the patch level override those defined at the root. When a patch is applied, any channel without an assigned preset is explicitly unset, meaning no sound will be produced on that channel.

Modulators and control¶

The SoundFont specification defines a set of default modulators (e.g. modulation wheel, channel volume, reverb send) that respond to standard MIDI Control Change (CC) messages. FluidSynth implements most of these defaults; see the FluidSynth control change implementation chart for details.

FluidPatcher does not expose a direct API for creating or modifying SoundFont modulators at runtime. However:

• NRPN messages can be used to access all SoundFont generators, as defined by the specification.
• Custom modulators can be authored directly in the SoundFont file using editors such as PolyPhone.

The ModSynth_R1.sf2 SoundFont included with this repository demonstrates custom modulators defined within the SoundFont itself.