The midi tracks were created by TuxGuitar so I think they're probably ok.

I ran $midimon.exe and it shows a few initial "Main Volume" commands before starting to play, and when I adjust the volume sliders on the mixer (or the track) I see midi "Main Volume" commands being issued - but no change in volume is heard. When I adjust the volume in the VSTi plugin I hear the volume change, but I see no midi "Main Volume" commands as a result. Looks like the plugin is ignoring MIDI volume commands and setting its own output volume.

Maybe I'm just unlucky in choosing three VSTi plugins that have this behaviour. I'm starting to expect weirdness from VSTi plugins now - one VSTi plugin (DrumTable) produces no sound at all until I tweak the base keys (C0 C1 etc) and even then I can't really be sure what sound should come out!

Anyway, I might just have to live with it. I'll do some more testing. Maybe my onboard audio is a POS.

PowerTracks Pro Audio 12
Onboard RealTek ALC883 audio