Hi !
Just recording and importing samples in .SF2 format are far from exhaustive sounds. In order to get an authentic grand piano sound, different zones have to be considered, which have to be processed in the YEM with different envelopes.
Each Grandpiano has different string zones (from single strings in the bass, up to three / four strings in the high registers), and each string zone responds differently to the release time. In the upper layers, most Grandpianos are undamped and the high layers generally sound. All this must be taken into account when programming in the YEM. The .SF2 format does not transport this data, therefore, despite external mappings with various tools, a lot of manual work in YEM necessary.
Greeting / Peter