Something’s really odd. I change the MIDI sound for the instrument, and it triggers a secondary note. Please check the SCREENCAST and advise what is causing this extra sound. It also appears that triggered note is the root of the Eb major key signature, even though the chart is in C minor.
If the extra note is significantly outside the normal range of the instrument, this sounds as if the extra note is a keyswitch. To let a keyswitch fulfill its purpose and not be audible, one must apply the proper expression map to tell the instrument how to interpret the keyswitch note.
Sometimes the VST/instrument publisher supplies the appropriate expression map, but sometimes they leave that job to the user.
Search here to see if an appropriate expression map exists for your instrument.
As @Derrek says, chances are you have an inappropriate expression map chosen in the Routing section of the Track Inspector panel in Play mode. If you’re manually choosing which sounds to use for an instrument, you also need to manually choose an appropriate expression map. Try choosing Default from the Ex. map drop-down.
For some reason, I now have two trumpet tracks in Play mode along with another pink track. Switching this track to Default map fixed the issue. However, the question is: why do I have two trumpet tracks and this extra track, and what is this extra track?