Just Updated to Build 458 and that has fixed this problem and other Midi playback issues when Transport not running. So I do not need to select a MIDI Output Driver now. Can leave it at <No MIDI/sound output> in MIDI/Audio Drivers Setup Window.
Build 458 bug fix - guess this was the one that fixed it:-
Fixed: The "ASIO Always On" setting for ASIO audio drivers was not working (ie MIDI output was silent if song not playing).

Last edited by Stratattack; 02/01/17 09:10 AM.