Notes sound very strange

Dear MuseScore,
I use Percussive Organ for my piano parts quite a lot and I noticed that the low A (bottom space of bass clef), A flat (bottom space of bass clef), and G sharp (bottom line of bass clef) do not sound at all like a percussive organ. Have you noticed this? If so, what can I do to get these notes to sound like a percussive organ?
In Him,

Thom