Foreign sounds in score

Please could someone have a look at the attached score for me? There is a low, sustained sound that plays through the whole score that isn’t notated and I don’t know where it is coming from.
This isn’t the first score I have come across that has ‘foreign’ sounds, particularly at the start. I don’t think it is a MIDI glitch as it is happening on several computers.
Many thanks
Musica_Foras (Dorico).zip (871 KB)

That usually means you’ve got MIDI keyswitches that are actually playing as notes instead of switches, because the wrong expression map is being used.

Do Play > Playback Templates and then select the HSSE Pro or Elements template, depending on which version you have installed. This will load the correct sounds and expression maps.

Brilliant, thank you.

As a follow up question, why does this happen in the first place? Surely when you open Dorico, the playback template should be correct automatically?
Incidentally, correct template was highlighted but when I clicked on another and then back onto it and applied, the sound expression maps etc. corrected themselves.

Normally this happens because you have changed one of the playback sounds directly in the HSSE plug-in, but then not told Dorico that you’ve done so (unfortunately it cannot know on its own). You then need to go to Endpoint Setup to change the expression map chosen for that sound.