pyfluidysnth users?

[drtquin]

Sadly I'm a Python programmer, not a C programmer.

I've made some good progress with a music teaching application based around pyfluidsynth, the Python Fluidsynth wrapper. However I now need to understand how in Python I can intercept events generated by a MIDI keyboard.

Any pointers to helpful sources much appreciated.

[mawe42]

Hi!

It would be easier to help if you could explain a bit more what you want to achieve. There are a few different ways to intercept and modify MIDI events before they are rendered by FluidSynth. The easiest way might be either the FluidSynth-internal MIDI router or an external application (like mididings, for example).

Cheers
Marcus

[drtquin]

Hello Marcus,

Many thanks for taking the time to reply.

I'm writing in Python and using a modified Pyfluidsynth library to talk to Fluidsynth. My C programming skills are not sufficient to implement a C based call-back function.

I want to pick up the MIDI message from a MIDI keyboard, do stuff with it (for instance update a graphical musical display), then pass on a possibly modified message to Fluidsynth via Pyfluidsynth.

Conceptually I think I need to replace fluid_synth_handle_midi_event() or implement handle_midi_event_func_t in Python.

Mididings looks interesting, however I'm working on Windows 10, so I don't think I can use it.

Cheers,

¬Jonathan

[jimhen3ry]

I write in C++ for Windows and I think I do something similar to what I think you want to do. In my case I take MIDI In and manipulate it to simulate a theatre pipe organ, including making a graphical display of the organ console that shows what the MIDI In is doing. I only use FluidSynth for the output. You can use FluidSynth's MIDI Channel Messages, such as fluid_synth_noteon, pretty much as a one-to-one replacement for MIDI Out messages. I have all the FluidSynth output paralleling Windows MIDI Out messages so that my program can be configured to output either MIDI or FluidSynth audio.

[drtquin]

Does sound similar, except that you're able to program in C++, whereas my skills are really only sufficient for Python. I've got around the problem by finding out how to stop Pyfluidsynth grabbing MIDI input, which then allows me to use Mido for MIDI input.

[jimhen3ry]

It sounds like your workaround is about the same as what I was suggesting. Use FluidSynth only for output. Stopping Pyfluidsynth grabbing MIDI input sounds more like a solution than a workaround.

[albedozero]

Hi @drtquin - I've contributed a decent amount to pyfluidsynth, and I've written my own Python FluidSynth wrapper as part of another project that implements a custom midi message router that I think does the kind of thing you're looking for. If you look at the linked function, as well as the Synth.__init__ function you should be able to see how the callback is set, but feel free to ask me questions if you're interested! I need to comment my code better...

[drtquin]

Hello Albedo Zero,

Excellent to hear from you. This is robust and professional work, but I think I'll need a bit of help to use it ;o(

• Is fswrap.py a replacement for pyfluidsynth? pyfluidsynth provides simple access to things like noteon and noteoff. I couldn't see equivalent calls in fswrap
• Can fswrap.py be used by itself, or does it need other packages in the fluidpatcher-0.4.2 directory?
• I added a couple of methods plus wrappers to pyfluidsynth to allow me to do some tuning to experiment with other than 12 tones per octave (eg 17 and 19):
  -- fluid_synth_activate_key_tuning
  -- fluid_synth_activate_tuning
  -- fluid_synth_deactivate_tuning
  -- I tried and failed to implement fluid_synth_tuning_dump
• Does fswrap provide access to the above tuning methods?
• What is the "linked function" you mentioned
• Might you have some basic example code?

Many thanks indeed.

[albedozero]

Either way should work - it was actually a bug in pyfluidsynth. The new_fluid_midi_driver function arguments were specified incorrectly, so your callback function couldn't match up - sometimes those ctypes errors are a bit cryptic. I updated the pyfluidsynth repo, but if you modify the same line in your code like this it should work for you.

[drtquin]

Hello Bill,

Almost there. With the change to new_fluid_midi_driver I can now get my own handler to work, so I can successfully intercept MIDI keyboard events and do my own thing with them.

I've added a parameter to fluidsynth.synth.Start() to allow me to pass in my custom handler: If I pass in "None" I want to revert to the default handler.

However the change new_fluid_midi_driver causes this line (from the original Start() method)
self.midi_driver = new_fluid_midi_driver(self.settings, fluid_midi_router_handle_midi_event, self.router)
to generate the error:
ctypes.ArgumentError: argument 2: <class 'TypeError'>: expected CFunctionType instance instead of CFunctionType

[albedozero]

Oops - I had the return types for the new_fluid_midi_driver and new_fluid_midi_router callbacks defined incorrectly. That first fix wasn't quite right, but if you make these changes in your fluidsynth.py it should work correctly. Also, make sure your custom router function returns FLUID_OK or FLUID_FAILED. Thanks for helping me track down my own 4-year old bug!

[drtquin]

Ah, the sweet sound of success! Very many thanks for your help.

All works but some rather ugly code:

fluidsynth.synth.Start() now looks like this:

    def start(self, driver=None, device=None, midi_driver=None, midi_router=None):
         <stuff>
         if midi_router == None:
            self.midi_driver = new_fluid_midi_driver(self.settings, fluid_midi_router_handle_midi_event, self.router)
        else:
            self.custom_router_callback = CFUNCTYPE(c_int, c_void_p, c_void_p)(midi_router)
            self.midi_driver = new_fluid_midi_driver(self.settings, self.custom_router_callback, self.router)

I've had to add half a dozen getter methods in pyfluidsynth to get the data from a MIDI event, so my midi_router looks like this:

def custom_midi_router(self, data, event):
        MIDI_NOTEOFF = 0x80
        MIDI_NOTEON = 0x90
        MIDI_CONTROL = 0xb0
        MIDI_VOLUME = 0x07
        type = self.fs.midi_event_get_type(event)
        velocity = 0
        key = 0
        value = 0
        if type == MIDI_NOTEOFF:
            midiKey = self.fs.midi_event_get_key(event) 
            self.fs.noteoff(0, midiKey)
            <stuff>
        elif type == MIDI_NOTEON:
            velocity = self.fs.midi_event_get_velocity(event)
            midiKey = self.fs.midi_event_get_key(event)
            self.fs.noteon(0, midiKey, velocity)
            <stuff>
        elif type == MIDI_CONTROL:
            control = self.fs.midi_event_get_control(event)
            value = self.fs.midi_event_get_value(event)
            <stuff>

        return fluidsynth.FLUID_OK

Thanks once again.

[albedozero]

Hey, whatever works! Happy to help. Make some awesome music!

[drtquin]

Hello Bill, Can I test your patience once again? Having successfully intercepted messages from a MIDI keyboard, I now want to do the same from a file. I can load and play a file using new_fluid_player(), fluid_player_add(), and fluid_player_play(), however rather than have fluidsynth play the file directly, I want to intercept the MIDI events. I think I can do this using the custom router call back we created for intercepting MIDI keyboard events. I’ve tried using this when creating the router, ie self.router = new_fluid_midi_router(self.settings, self.custom_router_callback, self.synth) However this seems to do nothing: it doesn’t crash and the player still plays the file. Guidance appreciated! A different question: I think I’ve broken something somewhere. When I play a note on my physical MIDI keyboard, or my virtual screen keyboard, I get a very short note. This is the case for both percussive (eg piano) and sustained (eg organ) instruments. Any thoughts? Very many thanks once again. ¬Jonathan From: Bill Peterson ***@***.***> Sent: 03 September 2021 21:08 To: FluidSynth/fluidsynth ***@***.***> Cc: drtquin ***@***.***>; Mention ***@***.***> Subject: Re: [FluidSynth/fluidsynth] pyfluidysnth users? (#958) Hey, whatever works! Happy to help. Make some awesome music! — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#958 (reply in thread)> , or unsubscribe <https://github.com/notifications/unsubscribe-auth/AU5HKYERQABX2IZ6R655M2LUAETLTANCNFSM5B6GGUFQ> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub> .

[albedozero]

Hi, Jonathan - no problem. I'll answer the second question first by saying I think you just need to grab the latest release of FluidSynth - the note-squashing sounds like #935, which was fixed in v2.2.2.

To get your player to send its events to your custom (or any) router, you just need to call fluid_player_set_playback_callback() on it, e.g.

fluid_player_set_playback_callback(self.player, self.custom_router_callback, self.synth)

When first created, the player's playback_callback is set to send directly to the synth by default, which is why you can hear it but your router has no effect.

[drtquin]

Hello Bill, Fantastic! 1. The latest download (2.2.3) did indeed solve the short note problem. I thought I’d broken something! 2. Your arguments for fluid_player_set_playback_callback(self.player, self.custom_router_callback, self.synth) did the trick. I’d started down this road, but got stuck because the third argument is different to that given at https://www.fluidsynth.org/api/group__midi__player.html#ga615cfa9d81227d9253dddebc49d8edcb I’m happy to share the work I (we) have done on fluidsynth.py. Is there an interest group or similar who might be interested? Very best, ¬Jonathan From: Bill Peterson ***@***.***> Sent: 20 September 2021 16:44 To: FluidSynth/fluidsynth ***@***.***> Cc: drtquin ***@***.***>; Mention ***@***.***> Subject: Re: [FluidSynth/fluidsynth] pyfluidysnth users? (Discussion #958) Hi, Jonathan - no problem. I'll answer the second question first by saying I think you just need to grab the latest release of FluidSynth - the note-squashing sounds like #935 <#935> , which was fixed in v2.2.2. To get your player to send its events to your custom (or any) router, you just need to call fluid_player_set_playback_callback() on it, e.g. fluid_player_set_playback_callback(self.player, self.custom_router_callback, self.synth) When first created, the player's playback_callback is set to send directly to the synth by default, which is why you can hear it but your router has no effect. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#958 (reply in thread)> , or unsubscribe <https://github.com/notifications/unsubscribe-auth/AU5HKYHRFIHQE5EWFVNVABTUC5JCPANCNFSM5B6GGUFQ> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub> .

[albedozero]

Sharing is very welcome! I think the best place to share would be on the main pyfluidsynth repo - that's where most of the (sporadic) development seems to be going on. You could start a discussion there, but the much slicker (and easier to manage) way would be to click the little fork button in the upper right-hand corner of the page, then copy and paste your changes into your own (now-forked) version of the pyfluidsynth repository. Github will then probably suggest you make a pull request, or you can click "contribute", and that request will show up in the main repo and we can do all our discussion/commenting/updating there.

[drtquin]

Shared as you suggest. Not sure if I've done the submission correctly. Thanks again.

[drtquin]

I'm trying to stop a file playing by calling fluid_player_stop() followed by delete_fluid_player(). However if there are notes playing when these methods are called, the notes continue to play. Which is a real problem when playing an organ piece!

[albedozero]

I noticed this recently too - if sustain or sostenuto are active when you stop/pause, the notes keep going, unless you also call fluid_player_seek(0). I've been discussing this with the maintainers in #981 and it might get simpler if my changes in #980 are added.

[drtquin]

Per the above, I'm using the fluid player to read in a MIDI file, and intercepting the events generated by the player.

I have a handle on most events being generated, however I'm not sure how to handle event 0x51. I think this means set tempo, however I can't see how to extract the tempo from the event.

Once I have the tempo, I assume I can set the tempo with fluid_player_set_tempo()

[albedozero]

It is a tempo change - you can extract it using any of the functions that get param1. For example fluid_midi_event_get_key, fluid_midi_event_get_velocity - there are several functions related to specific event types, but all they do is return the param1 member of the event struct. This is probably so some event-specific functionality could be included in future, but I'm not sure what that would be and I suspect it won't happen.

If you're not doing anything to modify an event/event type, you could just pass it on to fluidsynth's router by calling fluid_midi_router_handle_midi_event() at the end of your custom router function - no need to rewrite your own code to handle everything.

[drtquin]

Is this correct? Looking at https://www.recordingblogs.com/wiki/midi-set-tempo-meta-message suggests that the set tempo message has 3 bytes of data, not 1.

Also the value returned by eg fluid_midi_event_get_velocity() or fluid_midi_event_get_value() is 0.

With thanks.

[albedozero]

Oops my bad - fluid_midi_event_get_velocity and fluid_midi_event_get_value both return param2, so you would want to use e.g. fluid_midi_event_get_key. Tempo messages are indeed 3 bytes, but fluidsynth converts those bytes into a single integer for you and stores them in param1 here.

[drtquin]

Once again many thanks for your help.

A typical tempo value I get back is 0x35dac2. I've added a fluid_player_set_tempo() wrapper to fluidsynth.py, and I feed the tempo into this.

This method also takes a tempo_type parameter which can be one of

FLUID_PLAYER_TEMPO_INTERNAL 
FLUID_PLAYER_TEMPO_EXTERNAL_BPM 
FLUID_PLAYER_TEMPO_EXTERNAL_MIDI

I'm guessing these translate to integers 0, 1, 2, respectively (and that I want the third option), however it would be nicer to import these values from fluidsynth into fluidysnth.py.

Yet again my software ignorance: how can I do this?

[albedozero]

Values like that are defined as _enum_s in the C code, for example here - if values aren't specified for the constants they just get assigned 0, 1, 2, etc. so your assumption is correct. I don't think there's a way to export the values from the C code into python - easiest thing is just to define them yourself, for example

FLUID_PLAYER_TEMPO_INTERNAL = 0
FLUID_PLAYER_TEMPO_EXTERNAL_MIDI = 2

Here, INTERNAL means "use the tempo messages in the MIDI file", EXTERNAL means "change the tempo to a specific value I'm giving you". The first is the default, and fluidsynth will handle all the tempo updates - you don't have to parse the messages and call fluid_player_set_tempo yourself, unless you're trying to modify the tempo events. Your custom router function only needs to do things to the events you want to modify - the rest you can just pass on to fluid_midi_router_handle_midi_event for regular routing, or directly to fluid_synth_handle_midi_event and let fluidsynth do its thing.

[jbigdata-git]

Hi,

Working on DrumNotes an addon to Music21 to play drum parts, I dev a StreamPlayer full based on FluidSynth.
Among tests, this one do the job expected.
I use pyFluidSynth and achieve the adds to use FluidSynth 2.2.x, more efficient to callback MIDI events.

python3 fluidsynth_test.py and see 2 different callbacks to intercept MIDI events working.
...
playback_callback [140674764536352, 140674137616464, <class 'int'>].
playback_callback [140674764536352, 140674137616512, <class 'int'>].
...
tick_callback [140571333214544, 37880].
tick_callback [140571333214544, 37882].
...

Hope it can help.

JB.