Currently, gliss playback is limited to stepping by semitones. However, I have found a way to smooth things out, depending on your sample library.
- Create a Playing Technique that triggers the Playback Technique “Glissando Up” and “Glissando Down”.
- In your Expression Map, create a Base for Glissando Up / Down. Add CC20 (Portamento), with some suitable value. 80 worked for me. (You may need to turn on Legato controls, too.)
- Then use an actual gliss in conjunction with your Playing Technique. It’s a shame that the gliss doesn’t trigger the PTs by default. You can of course hide the Technique mark.
You’ll need another thing in the Ex Map to turn it off. Possibly Add CC20 : 0 to the Natural Base.
Depending on the instrument type and sample quality, the results may vary from risible to accurate.