I have a C code that creates a virtual synthesizer using FluidSynth. It loads a soundfont and connects the synthesizer to an external USB MIDI controller.

The code works perfectly on Debian. However, when I run it on a Raspberry Pi, the external MIDI controller fails to connect, and no error messages are displayed.

I’m using a Raspberry Pi Zero 2 W with Raspberry Pi OS 32-bit.

Note: If I manually connect the MIDI controller via shell using the command aconnect ‘Keystation Mini 32’:0 ‘fluid’:0, it works perfectly on the Raspberry Pi.

I can see the controller with aconnect -l and I add user to audio group with sudo usermod -a -G audio dimax
libasound2-dev libfluidsynth-dev, alsa-utils are installed.

Here’s the code:

#include <fluidsynth.h> 


//to compile: gcc -o test test.c `pkg-config fluidsynth --libs` -lm//

/*function that set the handler for midi event and allows communication between external midi controller and virtual synth*/
int fluid_synth_handle_midi_event(void *data,fluid_midi_event_t *event);

/*function to manage the reverb of the synth*/

int main(int argc, char **argv){
        /*define fluidsynth type to be used*/
    fluid_settings_t *settings = NULL;
    fluid_synth_t *synth = NULL;
    fluid_audio_driver_t *adriver = NULL;
    fluid_midi_driver_t* mdriver = NULL;    
    int sfont_id;
    int err = 0;
    /* Create the settings. */
    settings = new_fluid_settings();
    if(settings == NULL)
    {
        puts("Failed to create the settings!");
        goto err;
    }
    
 /*set midi autoconnect to automatically connect virtual synth to available midi ports*/
    fluid_settings_setint(settings,"midi.autoconnect",1);
/*create new synth instance*/
    synth = new_fluid_synth(settings);

    if(synth == NULL)
    {
        puts("Failed to create the synth!");
        goto err;
    }
    /*create midi driver using fluid_synth_handle_midi_event as handler*/
    mdriver = new_fluid_midi_driver(settings,fluid_synth_handle_midi_event, synth);
    if(mdriver == NULL){
        puts("Filed to create midi driver");
        goto err;}
    
   /* Create the audio driver. The synthesizer starts playing as soon
       as the driver is created. */
    adriver = new_fluid_audio_driver(settings, synth);
    if(adriver == NULL)
    {
        puts("Failed to create the audio driver!");
        goto err;
    }

    //INITIALIZE SOUNDFONTS//

    sfont_id = fluid_synth_sfload(synth,"synth1.SF2", 1);
    fluid_synth_noteon(synth, 0,60, 80);
    printf("press any key");
    getc(stdin);
    err:
   /*cleanup*/
   delete_fluid_audio_driver(adriver);
   delete_fluid_synth(synth);
   delete_fluid_settings(settings); 
   return 0;

}

Any ideas? Thank you in advance!

I’m trying to connect the external MIDI controller to the virtual synthesizer in FluidSynth with midi.autoconnect, but the connection fails.