audio-channels
int 1 1 128 By default, the synthesizer outputs a single stereo signal. Using this option, the synthesizer can output multi-channel audio. Sets the number of stereo channel pairs. So 1 is actually 2 channels (a stereo pair).
audio-groups
int 1 1 128 The output audio channel associated with a MIDI channel is wrapped around using the number of synth.audio-groups as modulo divider. This is typically the number of output channels on the sound card, as long as the LADSPA Fx unit is not used. In case of LADSPA unit, think of it as subgroups on a mixer.
chorus.active
bool 1 (TRUE) When set to 1 (TRUE) the chorus effects module is activated. Otherwise, no chorus will be added to the output signal. Note that the amount of signal sent to the chorus module depends on the "chorus send" generator defined in the SoundFont.
chorus.depth
num 8.0 0.0 256.0 Specifies the modulation depth of the chorus.
chorus.level
num 2.0 0.0 10.0 Specifies the output amplitude of the chorus signal.
chorus.nr
int 3 0 99 Sets the voice count of the chorus.
chorus.speed
num 0.3 0.1 5.0 Sets the modulation speed in Hz.
cpu-cores
int 1 1 256 Sets the number of synthesis CPU cores. If set to a value greater than 1, additional synthesis threads will be created to do the actual rendering work that is then returned synchronously by the render function. This has the affect of utilizing more of the total CPU for voices or decreasing render times when synthesizing audio. So for example, if you set cpu-cores to 4, fluidsynth will attempt to split the synthesis work it needs to do between the client's calling thread and three additional (internal) worker threads. As soon as all threads have done their work, their results are collected and the resulting buffer is returned to the caller.
default-soundfont
str C:\soundfonts\default.sf2 (Windows),
${CMAKE_INSTALL_PREFIX}/share/soundfonts/default.sf2 (all others) The default soundfont file to use by the fluidsynth executable. The default value can be overridden during compilation time by setting the DEFAULT_SOUNDFONT cmake variable.
device-id
int 0 0 127 Device identifier used for SYSEX commands, such as MIDI Tuning Standard commands. Fluidsynth will only process those SYSEX commands destined for this ID (except when this setting is set to 127, which causes fluidsynth to process all SYSEX commands, regardless of the device ID). Broadcast commands (with ID=127) will always be processed.
dynamic-sample-loading
bool 0 (FALSE) When set to 1 (TRUE), samples are loaded to and unloaded from memory whenever presets are being selected or unselected for a MIDI channel. PROGRAM_CHANGE and PROGRAM_SELECT events are typically responsible for this.
effects-channels
int 2 2 2 Specifies the number of effects per effects group. Currently this value can not be changed so there are always two effects per group available (reverb and chorus).
effects-groups
int 1 1 128 Specifies the number of effects groups. By default, the sound of all voices is rendered by one reverb and one chorus effect respectively (even for multi-channel rendering). This setting gives the user control which effects of a voice to render to which independent audio channels. E.g. setting synth.effects-groups == synth.midi-channels allows to render the effects of each MIDI channel to separate audio buffers. If synth.effects-groups is smaller than the number of MIDI channels, it will wrap around. Note that any value >1 will significantly increase CPU usage.
gain
num 0.2 0.0 10.0 The gain is applied to the final or master output of the synthesizer. It is set to a low value by default to avoid the saturation of the output when many notes are played.
ladspa.active
bool 0 (FALSE) When set to 1 (TRUE) the LADSPA subsystem will be enabled. This subsystem allows to load and interconnect LADSPA plug-ins. The output of the synthesizer is processed by the LADSPA subsystem. Note that the synthesizer has to be compiled with LADSPA support. More information about the LADSPA subsystem can be found in doc/ladspa.md or on the FluidSynth website.
lock-memory
bool 1 (TRUE) Page-lock memory that contains audio sample data, if true.
midi-channels
int 16 16 256 This setting defines the number of MIDI channels of the synthesizer. The MIDI standard defines 16 channels, so MIDI hardware is limited to this number. Internally FluidSynth can use more channels which can be mapped to different MIDI sources.
midi-bank-select
str gs gs, gm, xg, mma This setting defines how the synthesizer interprets Bank Select messages.

- gs: (default) CC0 becomes the bank number, CC32 is ignored.
- gm: ignores CC0 and CC32 messages.
- xg: if CC0<120 then channel is set to melodic and CC32 is the bank number. If CC0>=120 then channel is set to drum and the bank number is set to 128 (CC32 is ignored).
- mma: bank is calculated as CC0*128+CC32.

min-note-length
int 10 0 65535 Sets the minimum note duration in milliseconds. This ensures that really short duration note events, such as percussion notes, have a better chance of sounding as intended. Set to 0 to disable this feature.
overflow.age
num 1000.0 -10000.0 10000.0 This score is divided by the number of seconds this voice has been active and is added to the overflow priority. It is usually a positive value and gives voices which have just been started a higher priority, making them less likely to be killed in an overflow situation.
overflow.important
num 5000.0 -50000.0 50000.0 This score is added to voices on channels marked with the synth.overflow.important-channels setting.
overflow.important-channels
str (empty string) This setting is a comma-separated list of MIDI channel numbers that should be treated as "important" by the overflow calculation, adding the score set by synth.overflow.important to each voice on those channels. It can be used to make voices on particular MIDI channels less likely (synth.overflow.important > 0) or more likely (synth.overflow.important < 0) to be killed in an overflow situation. Channel numbers are 1-based, so the first MIDI channel is number 1.
overflow.percussion
num 4000.0 -10000.0 10000.0 Sets the overflow priority score added to voices on a percussion channel. This is usually a positive score, to give percussion voices a higher priority and less chance of being killed in an overflow situation.
overflow.released
num -2000.0 -10000.0 10000.0 Sets the overflow priority score added to voices that have already received a note-off event. This is usually a negative score, to give released voices a lower priority so that they are killed first in an overflow situation.
overflow.sustained
num -1000.0 -10000.0 10000.0 Sets the overflow priority score added to voices that are currently sustained. With the default value, sustained voices are considered less important and are more likely to be killed in an overflow situation.
overflow.volume
num 500.0 -10000.0 10000.0 Sets the overflow priority score added to voices based on their current volume. The voice volume is normalized to a value between 0 and 1 and multiplied with this setting. So voices with maximum volume get added the full score, voices with only half that volume get added half of this score.
polyphony
int 256 1 65535 The polyphony defines how many voices can be played in parallel. A note event produces one or more voices. Its good to set this to a value which the system can handle and will thus limit FluidSynth's CPU usage. When FluidSynth runs out of voices it will begin terminating lower priority voices for new note events.
reverb.active
bool 1 (TRUE) When set to 1 (TRUE) the reverb effects module is activated. Otherwise, no reverb will be added to the output signal. Note that the amount of signal sent to the reverb module depends on the "reverb send" generator defined in the SoundFont.
reverb.damp
num 0.0 0.0 1.0 Sets the amount of reverb damping.
reverb.level
num 0.9 0.0 1.0 Sets the reverb output amplitude.
reverb.room-size
num 0.2 0.0 1.0 Sets the room size (i.e. amount of wet) reverb.
reverb.width
num 0.5 0.0 100.0 Sets the stereo spread of the reverb signal.
sample-rate
num 44100.0 8000.0 96000.0 The sample rate of the audio generated by the synthesizer. For optimal performance, make sure this value equals the native output rate of the audio driver (in case you are using any of fluidsynth's audio drivers). Some drivers, such as Oboe, will interpolate sample-rates, whereas others, such as Jack, will override this setting, if a mismatch with the native output rate is detected.
threadsafe-api
bool 1 (TRUE) Controls whether the synth's public API is protected by a mutex or not. Default is on, turn it off for slightly better performance if you know you're only accessing the synth from one thread only, this could be the case in many embedded use cases for example. Note that libfluidsynth can use many threads by itself (shell is one, midi driver is one, midi player is one etc) so you should usually leave it on.
verbose
bool 0 (FALSE) When set to 1 (TRUE) the synthesizer will print out information about the received MIDI events to the stdout. This can be helpful for debugging. This setting cannot be changed after the synthesizer has started.
driver
str alsa (Linux),
dsound (Windows),
sndman (MacOS9),
coreaudio (Mac OS X),
dart (OS/2) alsa, coreaudio, dart, dsound, file, jack, oboe, opensles, oss, portaudio, pulseaudio, sdl2, sndman, wasapi, waveout The audio system to be used. In order to use sdl2 as audio driver, the application is responsible for initializing SDL's audio subsystem.
Note: sdl2 and waveout are available since fluidsynth 2.1.
periods
int 8 (Windows, MacOS9),
16 (all other) 2 64 The number of the audio buffers used by the driver. This number of buffers, multiplied by the buffer size (see setting audio.period-size), determines the maximum latency of the audio driver.
period-size
int 512 (Windows),
64 (all other) 64 8192 This is the number of audio samples most audio drivers will request from the synth at one time. In other words, it's the amount of samples the synth is allowed to render in one go when no state changes (events) are about to happen. Because of that, specifying too big numbers here may cause MIDI events to be poorly quantized (=untimed) when a MIDI driver or the synth's API directly is used, as fluidsynth cannot determine when those events are to arrive. This issue does not matter, when using the MIDI player or the MIDI sequencer, because in this case, fluidsynth does know when events will be received.
realtime-prio
int 60 0 99 Sets the realtime scheduling priority of the audio synthesis thread. This includes the synthesis threads created by the synth (in case synth.cpu-cores was greater 1). A value of 0 disables high priority scheduling. Linux is the only platform which currently makes use of different priority levels as specified by this setting. On other operating systems the thread priority is set to maximum. Drivers which use this option: alsa, oss and pulseaudio
sample-format
str 16bits 16bits, float The format of the audio samples. This is currently only an indication; the audio driver may ignore this setting if it can't handle the specified format.
alsa.device
str default ALSA device string, such as: "hw:0", "plughw:1", etc. Selects the ALSA audio device to use.
coreaudio.device
str default Selects the CoreAudio device to use.
coreaudio.channel-map
str (empty string) This setting is a comma-separated integer list that maps fluidsynth mono-channels to CoreAudio device output channels. Each position in the list represents the output channel of the CoreAudio device. The value of each position indicates the zero-based index of the fluidsynth output mono-channel to route there (i.e. the buffer index used for fluid_synth_process()). Additionally, the special value of -1 will turn off an output.
For example, the default map for a single stereo output is "0,1". A value of "0,0" will copy the left channel to the right, a value of "1,0" will flip left and right, and a value of "-1,1" will play only the right channel.
With a six-channel output device, and the synth.audio-channels and synth.audio-groups settings both set to "2", a channel map of "-1,-1,0,1,2,3" will result in notes from odd MIDI channels (audible on the first stereo channel, i.e. mono-indices 0,1) being sent to outputs 3 and 4, and even MIDI channels (audible on the second stereo channel, i.e. mono-indices 2,3) being sent to outputs 5 and 6.
If the list specifies less than the number of available outputs channels, outputs beyond those specified will maintain the default channel mapping given by the CoreAudio driver.
dart.device
str default Selects the Dart (OS/2 driver) device to use.
dsound.device
str default Selects the DirectSound (Windows) device to use.
file.endian
str 'auto' if libsndfile support is built in,
'cpu' otherwise. auto, big, cpu, little ('cpu' is all that is supported if libsndfile support is not built in) Defines the byte order when using the 'file' driver or file renderer to store audio to a file. 'auto' uses the default for the given file type, 'cpu' uses the CPU byte order, 'big' uses big endian byte order and 'little' uses little endian byte order.
file.format
str s16 double, float, s16, s24, s32, s8, u8 Defines the audio format when rendering audio to a file. Limited to 's16' if no libsndfile support.

- 'double' is 64 bit floating point,
- 'float' is 32 bit floating point,
- 's16' is 16 bit signed PCM,
- 's24' is 24 bit signed PCM,
- 's32' is 32 bit signed PCM,
- 's8' is 8 bit signed PCM and
- 'u8' is 8 bit unsigned PCM.

file.name
str 'fluidsynth.wav' if libsndfile support is built in,
'fluidsynth.raw' otherwise. Specifies the file name to store the audio to, when rendering audio to a file.
file.type
str 'auto' if libsndfile support is built in,
'raw' otherwise. aiff, au, auto, avr, caf, flac, htk, iff, mat, oga, paf, pvf, raw, sd2, sds, sf, voc, w64, wav, xi Sets the file type of the file which the audio will be stored to. 'auto' attempts to determine the file type from the audio.file.name file extension and falls back to 'wav' if the extension doesn't match any types. Limited to 'raw' if compiled without libsndfile support. Actual options will vary depending on libsndfile library.
jack.autoconnect
bool 0 (FALSE) If 1 (TRUE), then FluidSynth output is automatically connected to jack system audio output.
jack.id
str fluidsynth Unique identifier used when creating Jack client connection.
jack.multi
bool 0 (FALSE) If 1 (TRUE), then multi-channel Jack output will be enabled if synth.audio-channels is greater than 1.
jack.server
str (empty string) Jack server to connect to. Defaults to an empty string, which uses default Jack server.
oboe.id
int 0 0 2147483647 Request an audio device identified device using an ID as pointed out by Oboe's documentation.
oboe.sample-rate-conversion-quality
str None None, Fastest, Low, Medium, High, Best Sets the sample-rate conversion quality as pointed out by Oboe's documentation.
oboe.sharing-mode
str Shared Shared, Exclusive Sets the sharing mode as pointed out by Oboe's documentation.
oboe.performance-mode
str None None, PowerSaving, LowLatency Sets the performance mode as pointed out by Oboe's documentation.
oboe.error-recovery-mode
str Reconnect Reconnect, Stop Sets the error recovery mode when audio device error such as earphone disconnection occurred. It reconnects by default (same as OpenSLES behavior), but can be stopped if Stop is specified.
oss.device
str /dev/dsp Device to use for OSS audio output.
pipewire.media-category
str Playback The media category to use. This value will be passed to `PW_KEY_MEDIA_CATEGORY`, see Pipewire documentation for valid values.
pipewire.media-role
str Music The media role to use. This value will be passed to `PW_KEY_MEDIA_ROLE`, see Pipewire documentation for valid values.
pipewire.media-type
str Audio The media type to use. This value will be passed to `PW_KEY_MEDIA_TYPE`, see Pipewire documentation for valid values.
portaudio.device
str PortAudio Default Device to use for PortAudio driver output. Note that 'PortAudio Default' is a special value which outputs to the default PortAudio device. The format of the device name is: "<device_index>:<host_api_name>:<host_device_name>" e.g. "11:Windows DirectSound:SB PCI"
pulseaudio.adjust-latency
bool 1 (TRUE) If TRUE initializes the maximum length of the audio buffer to the highest supported value and increases the latency dynamically if PulseAudio suggests so. Else uses a buffer with length of "audio.period-size".
pulseaudio.device
str default Device to use for PulseAudio driver output.
pulseaudio.media-role
str music PulseAudio media role information.
pulseaudio.server
str default Server to use for PulseAudio driver output.
sdl2.device
str default Device to use for SDL2 driver output.
wasapi.device
str default Device to use for WASAPI driver output.
wasapi.exclusive-mode
bool 0 (FALSE) By default, WASAPI will operate in shared mode. Set it to 1 (TRUE) to use WASAPI in exclusive mode. In this mode, you'll benefit from direct soundcard access via kernel streaming, which has an extremely low latency. However, you must pay close attention to other settings, such as synth.sample-rate and audio.sample-format as your soundcard may not accept any possible sample configuration.
waveout.device
str default Device to use for WaveOut driver output.
autoconnect
bool 0 (FALSE) If 1 (TRUE), automatically connects FluidSynth to available MIDI input ports. alsa_seq, coremidi and jack are currently the only drivers making use of this.
driver
str alsa_seq (Linux),
winmidi (Windows),
jack (Mac OS X) alsa_raw, alsa_seq, coremidi, jack, midishare, oss, winmidi The MIDI system to be used.
realtime-prio
int 50 0 99 Sets the realtime scheduling priority of the MIDI thread (0 disables high priority scheduling). Linux is the only platform which currently makes use of different priority levels. Drivers which use this option: alsa_raw, alsa_seq, oss
portname
str (empty string) Used by coremidi and alsa_seq drivers for the portnames registered with the MIDI subsystem.
alsa.device
str default ALSA MIDI hardware device to use for RAW ALSA MIDI driver (not to be confused with the MIDI port). Since fluidsynth 2.3.0 this setting will be populated with available devices when fluidsynth starts up.
alsa_seq.device
str default ALSA sequencer hardware device to use for ALSA sequencer driver (not to be confused with the MIDI port).
alsa_seq.id
str pid ID to use when registering ports with the ALSA sequencer driver. If set to "pid" then the ID will be "FLUID Synth (PID)", where PID is the FluidSynth process ID of the audio thread otherwise the provided string will be used in place of PID.
coremidi.id
str pid Client ID to use for CoreMIDI driver. 'pid' will use process ID as port of the client name.
jack.server
str (empty string) Jack server to connect to for Jack MIDI driver. If an empty string then the default server will be used.
jack.id
str fluidsynth-midi Client ID to use with the Jack MIDI driver. If jack is also used as audio driver and "midi.jack.server" and "audio.jack.server" are equal, this setting will be overridden by "audio.jack.id", because a client cannot have multiple names.
oss.device
str /dev/midi The hardware device to use for OSS MIDI driver (not to be confused with the MIDI port).
winmidi.device
str default The hardware device to use for Windows MIDI driver (not to be confused with the MIDI port). Multiple devices can be specified by a list of devices index separated by a semicolon (e.g "2;0", which is equivalent to one device with 32 MIDI channels).
reset-synth
bool 1 (TRUE) If true, reset the synth after the end of a MIDI song, so that the state of a previous song can't affect the next song. Turn it off for seamless looping of a song.
timing-source
str sample sample, system Determines the timing source of the player sequencer. 'sample' uses the sample clock (how much audio has been output) to sequence events, in which case audio is synchronized with MIDI events. 'system' uses the system clock, audio and MIDI are not synchronized exactly.
prompt
str (empty string) In dump mode we set the prompt to "" (empty string). The ui cannot easily handle lines, which don't end with cr. Changing the prompt cannot be done through a command, because the current shell does not handle empty arguments.
port
int 9800 1 65535 The shell can be used in a client/server mode. This setting controls what TCP/IP port the server uses.