A soundfont files can be made up of Presets, Instruments and Samples. In the Yamaha EX5/7a Preset is more or less equivalent to a Voice, while an Instruments is called a Wave.
An Instrument has one or more Samples, and one ore more Instruments can be bundled in a Preset.
The present release of SF2S1 handels the Samples
of one Instrument at a time.
Most of the parameters that are on Sample and Wave level in the EX5/7 are copied,
such as loop points, key range, pan settings, tuning information, etc.
However, you need more to make a good souding
instrument, e.g. enveloppe parameters, modulation settings.
In the EX5/7 this information is stored on the preset level, different from the
SoundFont.
So, the Wave and Sample information that is saved in the S1M file is still very basic.
An Instrument like a piano, saved by SF2S1 can sound strange, even untuned, although the pitch parameters (root key, coarse and fine tune) are copied.