I have an arsenal of external analog synths, most of which are monophonic and/or monotimbral. I want to set them up as External Instruments (for proper delay compensation, etc), record and edit MIDI, then Freeze the MIDI to audio, and proceed to record another track using that same synth. However, the Freeze function is NOT unloading the External Instrument VST, even tho the “Unload Instrument when Frozen” is checked, and this prevents any more Instrument tracks from being created for that synth. 
This is clearly a BUG, as it is not behaving as advertised (Unloading) and not behaving the same as other VST instruments.
To recreate:
- define an External Instrument, incl. MIDI and audio routing to an external synthesizer
- create an Instrument track using that External Instrument
- record some MIDI on that track
- Freeze the track, with “Unload Instrument when Frozen” checked
→ Result: audio is rendered from the MIDI, as expected, but the External Instrument is NOT unloaded and thus cannot be used again.
The very ugly workaround is to go back to managing the MIDI and audio as separate tracks and manually rendering MIDI to audio, muting the MIDI track, etc., instead of using Cubase’s otherwise very elegant Instrument tracks. Eww…
System:
- Macbook Pro 15" (current model), 16GB RAM, 1TB SSD
- RME Fireface UFX + RME ADI DS
- Mac OS X 10.11.6
- External synths: ARP Odyssey, Moog Voyager, OB-6, Prophet-6, Prophet-12, Hammond Xk-1c, MOTU Micro Lite
- Cubase 8.5.20
ps - minor quibble, but IMHO, in the list of available VSTs, External Instruments should be a top-level category, not buried within the Steinberg category. For one, this makes them easier to find - after all, External Instruments are not made by Steinberg, but by other companies - and it more naturally matches the External Instruments tab in the VST Connections dialog box, too.