Ardour 3.1 only plays plugins while stopped?

I recently paid to download Ardour 3.1 (yeah, building from source just wasn’t going to happen). I’ve finally got my Akai MPK Mini, as well as a couple of LV2 synths working. I also run Hydrogen (synced) as a tool to use alongside Ardour.

However, whether the MIDI track is armed or disarmed to record, when I press play in Ardour (which triggers Hydrogen), I have no output from the synth. Then if I hit the stop button, I hear the synth again.

Is this an intentional/overlooked decision, or do I just have to adjust a setting somewhere?

some work has been done in this area since 3.1 (are you sure you got 3.1 “recently”? or later version?). however it is not entirely clear what the issue is here. when the transport is rolling, a track will deliver either its input signal or the signal from disk to its processing chain (which is where a synth plugin lives). if you’re not using 3.3, upgrade and check that. if you are using 3.3, then maybe a bit more explanation of what you expect to happen would be good.

I suspect what you mean by “no output from the synth” is that you do not hear any sound from the synth by playing your keyboard when Ardour is playing. This is curently how Ardour works. Midi input is disabled while Ardour plays unless you are recording that midi track. However, you should hear output if you have recorded midi to the midi track - that should be played back when you hit play. This has to do with how Ardour is set up to do monitoring. I think there is a plan to change this monitoring setup at some point.

Would it be possible, then, to run the synths as standalone outside of Ardour (to be triggered by the keyboard)? I assume I would just create an audio track instead of a midi track? However, at that point, quantizing is out of the question.

In general you can plays synths outside of Ardour using a keyboard. (though you should able to play your synth in Ardour if you are recording the midi track which contains the synth). Some synths are available as standalone Jack applications but others are plugins and need to be run by a plugin host of which there are several depending on the plugin type. Carla (from kxstudio) can run any type of plugin (lv2, dssi, linux vst, windows vst) is the best general choice. Jalv can run lv2, jack-dssi-host can run dssi, and festige can run windows vsts.

This thread confused me. See

You CAN play a synth live while the track is running, just click the “In” button on the mixer string. This sets it to always only listen to midi in, and not the track contents. You can click “In” again to go back to auto mode, which switches between “in” when stopped or recording, and “disk” when playing back.