VMS-like MIDI Out driver for FluidSynth ?

[klerg]

Hello

Is there a MIDI Out driver like VirtualMIDSynth that supports FluidSynth and works on Linux or Windows ?

Thanks a lot

[jimhen3ry]

You can use a command line to open FluidSynth to receive MIDI input. Here is an example that uses the Windows WASAPI driver for audio output and a loopMIDI virtual MIDI cable for MIDI IN:
fluidsynth -a wasapi -m winmidi -b 25 -o midi.winmidi.device="1:loopMIDI-1" gm.sf2

QSynth might be what you are really looking for.

[klerg]

I did not know this, but my aim is to avoid the command line of Fluidsynth. I can see why WASAPI is chosen in this case, but what do all of the 'flags' like -m, winmidi, -b, 25, and -o mean here ?

Qsynth is a GUI for FluidSynth what is a MIDI Out driver like VirtualMIDISynth ?

[MaMohm]

This is a common confusion because "drivers" and "synthesizers" are often bundled together on Windows (like VirtualMIDISynth), but kept separate in the professional audio world (and on Linux).

Here is the breakdown of the flags you asked about, followed by the solution to get a GUI-based "driver" experience.

1. Decoding the Command Line Flags
   The command jimhen3ry provided is configuring FluidSynth to run with very specific hardware settings. Here is what each flag does:

-a wasapi (Audio Driver): This tells FluidSynth how to talk to your sound card. WASAPI (Windows Audio Session API) is a modern Windows driver that provides much lower latency (delay) than the older DirectSound driver.

-m winmidi (MIDI Driver): This tells FluidSynth how to listen for notes. winmidi is the standard Windows MIDI interface.

-o midi.winmidi.device="1:loopMIDI-1" (Option): The -o flag allows you to set internal settings manually. Here, it is forcing FluidSynth to listen specifically to the "loopMIDI" port (a virtual cable) rather than just any random MIDI device.

-b 25 (Buffer): This likely sets the audio buffer count or size (though in modern versions, this is often handled by -z or -c). A lower number means less delay (latency) between pressing a key and hearing sound, but it requires more computer power.

2. The Solution: How to Avoid the Command Line
   You don't need a single "FluidSynth Driver" to achieve what you want. You simply need to replicate what VirtualMIDISynth does by chaining two tools together.

VirtualMIDISynth is actually two things in one box: a Virtual MIDI Cable + a Synthesizer. To use the FluidSynth engine instead, you just separate them.

On Windows (The "Combo" Method)
Since FluidSynth doesn't come as a system "driver," you create a permanent bridge.

Install a Virtual Cable: Download loopMIDI (free). create a port named "FluidSynth In". This acts as the "Driver" that will show up in your games/DAWs.

Install the GUI: Download QSynth. This is the graphical version of FluidSynth. You use buttons and menus instead of typing commands.

Connect them:

Open QSynth.

In Setup > MIDI, select "loopMIDI" as your input device.

In Setup > Audio, select "WASAPI" (for fast audio).

Load your SoundFont (SF2) in the Soundfonts tab.

Now, whenever you select "loopMIDI" in your music software, QSynth will play the sound using the FluidSynth engine, and you never have to touch a command line.

On Linux (The Native Way)
Linux is much easier because the architecture is designed for this. You do not need a virtual cable driver.

Install QSynth: (sudo apt install qsynth on Debian/Ubuntu).

Run it: When QSynth starts, it automatically registers itself as a MIDI destination in the system (ALSA).

Connect: Any Linux MIDI app (Rosegarden, MuseScore, etc.) will immediately see "FluidSynth" or "QSynth" as a valid MIDI Output device in their settings. No extra drivers needed.

[klerg]

This is true as it is so common to find "drivers" and "synthesizers" are many times combined as one, though this was not always the case. At first, they used to be separate but 'loopback' cables brought both together.

Nice, as it is best to know what the flags are going to do before I type them out in the command line. Yes, that will help as well.

1. I see and did assume that the command asks for FluidSynth to use very detailed settings but not sure just what those are, let's find out:

I pretty much knew what -a wasapi does as -a means the audio driver and wasapi, of course, is the audio driver itself, and I will use wasapi as that gives low latency, I forgot just how much that actually is but it has less than half of Directsound

I was not too sure what this command is meant to be but it looks like it tells Fluidsynth to use a Windows MIDI driver then.

This command is probably the most involved then all of the rest as it instructs Fluidsynth to only take up nothing but the 'loopMIDI' virtual MIDI port and not allow any other MIDI input device to work here. So it is the key ingredient as such.

My guess is -b means buffer and 25 is the latency in ms, but it seems I was wrong on the second part as that is the audio buffer count or size then. Well, I hope 25 equals the same amount in latency in ms, and will not consume too much power.

2. Sure my goal is to stay away from command line
   This is what I really did not know in the first place but I will take note of that. Well, I had no idea that VirtualMIDISynth just uses two tools as one, and is interesting to say the least.

Wow, I had no clue that VirtualMIDISynth is actually a virtual MIDI cable and synthesizer rolled into one. That means we can replicate what it does one way or another.

Appreciate it, the step by step instructions for loopMIDI and QSynth on Linux and Windows, and notice it is a bit simpler on the former.

I only wish a newer binary for Qsynth was available for Windows but it is good enough

[derselbst]

This is the first time I'm seeing an AI generated answer being accepted. It is mostly correct. Interestingly, all AI models I've tried assume that -b has something to do with the buffer. It doesn't. It specifies the bank offset, which presumably isn't what @jimhen3ry intended. Pls. refer to the UserManual.

[klerg]

I had a feeling that this answer was AI generated as it is just too long. That is good to know. Well, that is a pretty big mistake to make as -b has nothing to do with the buffer it seems. That is right. Bank offset is quite far from buffer. Is there anywhere else that this AI response might be off or is wrong ?

[jimhen3ry]

Yes, -b 25 is a bank offset. I just grabbed the command line I use to test external MIDI output from the Miditzer to give klerg an idea of what it takes to have FluidSynth accept MIDI In. The Miditzer uses a bank offset of 25 for historical reasons that may not have been necessary even at the outset.

[klerg]

That bank offset is often in use. Yes that is a handy command I will take a note of it as gives a good example of how to make FluidSynth to work with MIDI In for the most part too. I see it looks like Miditzer does not need a bank offset of 25 but it is a bit too late for any change to the way that is.