Issues with Dorico Playback

I’ve started experiencing some issues with the playback on Dorico Pro. For whatever reason, it won’t play the lower notes of an instrument register, sometimes the playback using the p key doesn’t work and sometimes I’ll try to click on pitches to hear them individually and I get this weird trilling sound. How would I fix that?

What instrument produces this result, and what VST (HALion? NotePerformer?) produces the sounds?

I’m having issues with the alto flute not playing below B natural and i think i’m using the HALion for the sound library.

IIRC Written B below the staff would be the Alto Flute’s lowest possible note (sounding F# down a fourth), and that would be a stretch, since written “middle” C is generally considered the Alto Flute’s lowest note.

But if the score is written in C and not transposed the Alto flute should theoretically play as low as G below middle C, so i don’t understand why the flute wouldn’t play those exact pitches.

Yes, in a concert-pitch score, the Alto Flute should play down to G below middle C. The reason it does not is that the HALion Player uses Flute Combi (a regular flute) to produce the Alto Flute sound, and the regular Flute only goes down to B. Using the GM Flute from HALion SE will give you the missing pitches (plus pitches outside the actual range). Of course the sound may not be as realistic.

NotePerformer will also give you the full range.