Section: User Commands (1)
Updated: Feb 16, 2020
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FluidSynth - a SoundFont synthesizer  


fluidsynth [options] [ SoundFonts ] [ midifiles ]  


FluidSynth is a real-time MIDI synthesizer based on the SoundFont(R) 2 specifications. It can be used to render MIDI input or MIDI files to audio. The MIDI events are read from a MIDI device. The sound is rendered in real-time to the sound output device.

The easiest way to start the synthesizer is to give it a SoundFont on the command line: 'fluidsynth soundfont.sf2'. fluidsynth will load the SoundFont and read MIDI events from the default MIDI device using the default MIDI driver. Once FluidSynth is running, it reads commands from the stdin. There are commands to send MIDI events manually, to load or unload SoundFonts, and so forth. All the available commands are discussed below.

FluidSynth can also be used to play a list of MIDI files. Simply run FluidSynth with the SoundFont and the list of MIDI files to play. In this case you might not want to open the MIDI device to read external events. Use the -n option to deactivate MIDI input. If you also want to deactivate the use of the shell, start FluidSynth with the -i option: 'fluidsynth -ni soundfont.sf2 midifile1.mid midifile2.mid'.

Run fluidsynth with the --help option to check for changes in the list of options.  


fluidsynth accepts the following options:

-a, --audio-driver=[label]
The audio driver to use. "-a help" to list valid options
-c, --audio-bufcount=[count]
Number of audio buffers
-C, --chorus
Turn the chorus on or off [0|1|yes|no, default = on]
-d, --dump
Dump incoming and outgoing MIDI events to stdout
-E, --audio-file-endian
Audio file endian for fast rendering or aufile driver ("-E help" for list)
-f, --load-config
Load command configuration file (shell commands)
-F, --fast-render=[file]
Render MIDI file to raw audio data and store in [file]
-g, --gain
Set the master gain [0 < gain < 10, default = 0.2]
-G, --audio-groups
Defines the number of LADSPA audio nodes
-h, --help
Print out this help summary
-i, --no-shell
Don't read commands from the shell [default = yes]
-j, --connect-jack-outputs
Attempt to connect the jack outputs to the physical ports
-K, --midi-channels=[num]
The number of midi channels [default = 16]
-l, --disable-lash
Don't connect to LASH server
-L, --audio-channels=[num]
The number of stereo audio channels [default = 1]
-m, --midi-driver=[label]
The name of the midi driver to use. "-m help" to list valid options.
-n, --no-midi-in
Don't create a midi driver to read MIDI input events [default = yes]
Define a setting, -o name=value ("-o help" to dump current values)
-O, --audio-file-format
Audio file format for fast rendering or aufile driver ("-O help" for list)
-p, --portname=[label]
Set MIDI port name (alsa_seq, coremidi drivers)
-q, --quiet
Do not print welcome message or other informational output
-r, --sample-rate
Set the sample rate
-R, --reverb
Turn the reverb on or off [0|1|yes|no, default = on]
-s, --server
Start FluidSynth as a server process
-T, --audio-file-type
Audio file type for fast rendering or aufile driver ("T help" for list)
-v, --verbose
Print out verbose messages about midi events (synth.verbose=1) as well as other debug messages
-V, --version
Show version of program
-z, --audio-bufsize=[size]
Size of each audio buffer



The settings to be specified with -o are documented in the fluidsettings.xml hopefully shipped with this distribution or online at http://www.fluidsynth.org/api/fluidsettings.xml . We recommend viewing this file in a webbrowser, favourably Firefox.



Prints out list of help topics (type "help <topic>" to view details on available commands)
Quit the synthesizer
load filename
Load a SoundFont
unload number
Unload a SoundFont. The number is the index of the SoundFont on the stack.
Lists the current SoundFonts on the stack
inst number
Print out the available instruments for the SoundFont.
noteon channel key velocity
Send a note-on event
noteoff channel key
Send a note-off event
cc channel ctrl value
Send a control change event
prog chan num
Send program-change message
select chan sfont bank prog
Combination of bank-select and program-change
Print out the presets of all channels.
gain value
Set the master gain (0 < gain < 5)
interp num
Choose interpolation method for all channels
interpc chan num
Choose interpolation method for one channel
set synth.reverb.active [0|1]
Turn the reverb on or off
set synth.reverb.room-size num
Change reverb room size
set synth.reverb.damp num
Change reverb damping
set synth.reverb.width num
Change reverb width
set synth.reverb.level num
Change reverb level
set synth.chorus.active [0|1]
Turn the chorus on or off
set synth.chorus.nr n
Use n delay lines (default 3)
set synth.chorus.level num
Set output level of each chorus line to num
set synth.chorus.speed num
Set mod speed of chorus to num (Hz)
set synth.chorus.depth num
Set chorus modulation depth to num (ms)
Reloads the default MIDI routing rules (input channels are mapped 1:1 to the synth)
Deletes all MIDI routing rules.
router_begin [note|cc|prog|pbend|cpress|kpress]
Starts a new routing rule for events of the given type
router_chan min max mul add
Limits the rule for events on min <= chan <= max. If the channel falls into the window, it is multiplied by 'mul', then 'add' is added.
router_par1 min max mul add
Limits parameter 1 (for example note number in a note events). Similar to router_chan.
router_par2 min max mul add
Limits parameter 2 (for example velocity in a note event). Similar to router_chan
Finishes the current rule and adds it to the router.
Router examples
router_begin note
router_chan 0 7 0 15
Will accept only note events from the lower 8 MIDI
channels. Regardless of the channel, the synthesizer plays the note on ch 15 (synthchannel=midichannel*0+15)
router_begin cc
router_chan 0 7 0 15
router_par1 1 1 0 64
Configures the modulation wheel to act as sustain pedal (transforms CC 1 to CC 64 on the lower 8 MIDI channels, routes to ch 15)



Peter Hanappe <hanappe@fluid-synth.org>
Markus Nentwig <nentwig@users.sourceforge.net>
Antoine Schmitt <as@gratin.org>
Josh Green <jgreen@users.sourceforge.net>
Stephane Letz <letz@grame.fr>
Tom Moebert <tom[d0t]mbrt[√ĄT]gmail[d0t]com>

Please check the AUTHORS and THANKS files for all credits  


SoundFont(R) is a registered trademark of E-mu Systems, Inc.