I would guess that Arne’s presets for NotePerformer don’t include the upright bass instrument, which we added relatively recently. I expect he’ll fix this in a future NotePerformer update.
if you change the upright bass to fretless bass you’ll get the acoustic bass sound (doesn’t matter which one you choose, 4, 5 ot 6 stringed.)
But I’d REALLY lika Arne to develop a Jazz edition of NotePerformer. Everything sounds just magnificent, but NP interprets the music in a very idiomatic classical way. So “just” a little tweak on how NP interprets articulations and also possibility to add the tenuto feature as in Sibelius.