Can't monitor VST instrument during audio track playback [solved]


I’ve been using Ardour for a couple of years now, and for some reason I have never had this issue until now. Here is what happens in Ubuntu 18.04:

  1. I record an audio track, and all is fine.

  2. I add a MIDI track with a VST instrument (e.g. Yoshimi). I can play the VST instrument using my external MIDI keyboard. All is fine.

  3. I start playback to play along to the already recorded audio track. This is what happens:

  • There is no sound from the VST instrument when playing my external or virtual keyboard.
  • When I record enable the track, I can see that MIDI data are received on the track, but still no sound from the VST instrument, but the audio track is playing just fine.
  • When I hit record and start recording, suddenly there is sound from the VST instrument as I play along to the audio.
  • I stop recording and hit play: There is sound from the MIDI VST instrument track and the audio track.

To sum up: While listening back to recorded audio, I can only seem to monitor any input to VST instruments when actually recording. Rather, I would like to be able to playback the audio, so that I can mess about with different ideas before I actually record my MIDI data. I’ve made a short screen recording of what happens, if that is clearer than my explanation here. Any help would be much appreciated! The problem is the same no matter if using ALSA or Jack.

Link to screen recording:
Audio/Midi playback/monitoring conflict

Many thanks in advance.

In Ardour 5 this is normal behavior. On a given track, you can either monitor Input or Playback from disk.

Watch the “In” and “Disk” buttons on the mixer-strip (next to the record-arm).

You can explicitly select one (the button becomes fully lit). Otherwise the setting is implicit (yellow outline) depending on preferences and state (rec-arm’ed, recording, playing).

A common setup is to use a MIDI-bus with the instrument.

Then use various MIDI-Tracks without an instrument-plugin and change all these to monitor Disk. Connect the MIDI-out of those tracks to the MIDI-bus’ input.
Finally also connect your midi-keyboard to both: the Track(s) and the Bus.

  • When you play live, you directly play the instrument on the bus (and can hear yourself).
  • All other MIDI tracks will only always play data from disk (if any) and yo can individually mute them
  • You can record to those tracks (but still hear yourself via the direct bus connection)

As additional advantage, there’s only one synth plugin (saves resources)

Well, that was embarrassingly straight-forward. All works perfectly now. Thanks!

Regarding the MIDI bus solution … Perhaps I am a bit slow, but wouldn’t it require as many buses w/synth plugin as there are MIDI tracks? I.e., what is the advantage from a resource perspective of placing the synth plugins on buses (to which corresponding MIDI tracks are routed), rather than placing them directly on the MIDI tracks? Unless, of course, I wanted several separate MIDI tracks to control one instance of the same synth plugin on one of the buses? I’m probably missing something here, so please forgive me if my question misses the target.

Yes, this. Most MIDI synths support 16 MIDI channels, so up to 16 different sounds.

In theory you can also use a single MIDI track to record/play all 16 MIDI channels, but in practice it’s a lot easier to use separate tracks for different instruments.

I mostly mentioned this as easy way to have both: playback from disk and simultaneous live input in Ardour 5.x. using the same synth.

PS. Ardour 6 will allow to enable “Disk” and “In” simultaneously and mix signals.

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Cool! I’ll look into that possibility. Looking forward to Ardour 6 when it is ready for the masses. Keep up the nice work you’re doing!