The mysterious "freeze" feature, and caching audio of a MIDI software instrument track to lower CPU usage

MIDI software instrument tracks can use a lot more CPU than audio tracks. It would be great if there ware a feature to render an audio version of a MIDI track, which would take the place of the MIDI track until something in the MIDI track were edited, in which case the audio would become “stale”, and Ardour should switch back to playing the MIDI.

I’ve read some posts which mention a feature called “freeze”, but I can’t find much information about it in the manual. Does this feature do something similar to what I’ve described? Can someone please explain what it does?


In Cubase, Reaper, and other DAW’s, “Freeze” does exactly what you think it does. It renders an audio track in place of the MIDI track to free up the CPU. It is just another name for render in place, or bounce. You have to ‘unfreeze’ to edit the MIDI, then freeze again to re-render with the edits.

As far as I know, there is currently no ‘freeze’ or ‘render in place’ feature in the latest Ardour. It can easily we worked around by selecting ‘Session → Export → Stem Export’ from the main menu bar. In windows the shortcut in SHFT-ALT-E As you can see in the picture below, you can select which tracks to export. Make sure you select ‘Re-import Exported Audio’ before exporting. This will create a new track with all the selected STEMS rendered.

It saves lot of disk space compared to ‘freeze’ and ‘render’ when you export using Alt-E , or Session → Export → Export to Audio Files. It renders 1 freeze file with all them mixed instead of one file for each individual track as it would using STEM Export.

After that. you can deactivate the MIDI tracks by selecting all the tracks you want to deactivate with shift+left-click. Then, right-click, and you can uncheck ‘Active’. This will deactivate the selected tracks. See last picture for a close up.

I was only able to upload 1 picture to my post, that is why they are small.

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There is “Bounce (with processing)” and “Bounce (without processing)” feature:


In other DAWS there is one track type, where you can put both Audio and MIDI clips. So you can put an bounced/freezed audio clip on the same track.

In Ardour we have separate MIDI and Audio track types, so you have to put the bounced clips onto a
different audio track. So “render in place” will never be available, I think.

And the bounce is per clip, not per track, so if you bounce multiple selected MIDI clips, you get multiple bounced audio clips. So if you want to bounce whole track you can use a lua script that @johndev is talking about or combine the clips before bouncing (and uncombine after). :slight_smile:

@toxonic recently wrote a Lua script to make life even easier, as it can also undo the freeze for example. I haven’t tried it myself yet but would be worth a look.

Ah, I see why you say “render in place” will probably never be available. It would be handy in order to keep the same fader automation, effects, etc. on the rendered audio track as were on the MDI track, but I am glad to hear that you can get most of the way there by the suggestions in this thread.

Thanks, this is all very helpful!

For this purpose you have the “Bounce (with processing)” option which includes automation and effects.

BTW: I tried the “bounce (without processing)” and I don’t get what is this for. As the result I get empty audio clip files, every time I use this.

Do any of you know what it is for? :slight_smile:

It adds the bounced file to the Editor (Shift-L) or View->Show Editor List under the Sources tab.

Make sure you are on the EDIT page.

The manual is available at this link.

Bounce with processing will give an audio file when bouncing MIDI.

Bounce with no processing will give a MIDI file when bouncing MIDI, because it will not go through the plug ins.

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