Synthesizer settings audio-channels int 1 1 128 By default, the synthesizer outputs a single stereo signal. Using this option, the synthesizer can output multichannel audio. Sets the number of stereo channel pairs. So 1 is actually 2 channels (a stereo pair). audio-groups int 1 1 128 Normally the same value as synth.audio-channels. LADSPA effects subsystem can use this value though, in which case it may differ. 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. cpu-cores int 1 1 256 (Experimental) Sets the number of synthesis CPU cores. If set to a value greater than 1, then additional synthesis threads will be created to take advantage of a multi CPU or CPU core system. This has the affect of utilizing more of the total CPU for voices or decreasing render times when synthesizing audio to a file. device-id int 0 0 126 Device identifier used for SYSEX commands, such as MIDI Tuning Standard commands. Only those SYSEX commands destined for this ID or to all devices will be acted upon. effects-channels int 2 2 2 Currently unused. 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 "yes" 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 later. 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 gm, gs, xg, mma This setting defines how the synthesizer interprets Bank Select messages.

• gm: ignores CC0 and CC32 messages.
• gs: (default) CC0 becomes the bank number, CC32 is ignored.
• xg: CC32 becomes the bank number, CC0 toggles between melodic or drum channel.
• 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 -10000 10000 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 -50000 50000 This score is added to voices on channels marked with the synth.overflow.important-channels setting. overflow.important-channels str "" 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 -10000 10000 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 -10000 10000 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 -10000 10000 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 -10000 10000 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. parallel-render bool 1 (TRUE) This is the low-latency setting. If on, you're allowed to call fluid_synth_write_s16, fluid_synth_write_float, fluid_synth_nwrite_float or fluid_synth_process in parallel with the rest of the calls, and it won't be blocked by time intensive calls to the synth. Turn it off if throughput is more important than latency, e g in rendering-to-file scenarios where underruns is not an issue. As of 1.1.7 this option is deprecated. This option enforces thread safety for rvoice_mixer, which causes rvoice_events to be queued internally. The current implementation relies on the fact that this option is set to TRUE to correctly render any amount of requested audio. Also calling fluid_synth_write_* in parallel is not considered to be a use-case. It would cause undefined audio output, as it would be unpredictable for the user which rvoice_events specifically would be dispatched to which fluid_synth_write_* call. 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. sample-rate num 44100.0 22050.0 96000.0 The sample rate of the audio generated by the synthesizer. 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. Also see synth.parallel-render. 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. MIDI driver settings autoconnect bool 0 (FALSE) If 1 (TRUE), automatically connects FluidSynth to available MIDI input ports. alsa_seq is currently the only driver 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 Used by coremidi and alsa_seq drivers for the portnames registered with the MIDI subsystem. alsa.device str default ALSA MIDI device to use for RAW ALSA MIDI driver. alsa_seq.device str default ALSA sequencer device to use for ALSA sequencer driver. 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 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 Device to use for OSS MIDI driver. winmidi.device str default Device for Windows MIDI driver. MIDI player settings reset-synth bool 1 (TRUE) If true, reset the synth before starting a new MIDI song, so the state of a previous song can't affect the new 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. Shell (command line) settings prompt str "" In dump mode we set the prompt to "". 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 num 9800 1 65535 The shell can be used in a client/server mode. This setting controls what TCP/IP port the server uses.