The Triangle Combi Key patch only includes the open and roll sounds – if you open the HALion Sonic SE interface and select the Triangle Combi Key channel, you’ll see there’s a single octave of sounds mapped, and the lower half of the octave provides a normal hit, while the upper half of the octave provides a roll. No muted sound is provided.
However, if you use the standard drum kit, you can use MIDI notes 80 and 81 for muted and open sounds respectively, but you’ll get no roll in that case. To use these sounds:
- In the channel that currently has Triangle Combi Key loaded in HSSE, load [GM 129] Stereo GM Kit (or another compatible kit of your choice).
- In the track header for the triangle instrument in Play mode, click the cog button to open the Endpoint Setup dialog, and set the Percussion Map column for the channel with your triangle loaded to Yamaha XG (instead of HSO Triangle Combi Key).
- In Setup mode, expand the player card for the player assigned the triangle instrument, and hover over the instrument label in the expanded card so that the chevron > appears. Click the label and from the context menu that appears choose Edit Percussion Playing Techniques.
- In the Edit Percussion Playing Techniques dialog, add a new mapping by clicking the + button. Add a mapping for the Muted playback technique, and choose an appropriate notehead: I chose X Notehead.
That should be it: now, for an open triangle note, use a normal notehead, and for a muted one, type Alt+up/down during note input to choose the Muted technique, which will produce the notehead of your choice (e.g. in my case, the X notehead) as well as the expected playback sound.