Here's how it works:
1. Depack the 2sflib into bin file - Neill's psf2exe won't work, but VGMToolbox (http://sourceforge.net/projects/vgmtoolbox/
) handles it fine (Misc. Tools -> xSF Tools -> xSF2EXE).
2. Strip first 8 bytes of the bin file (4 bytes for load adress, 4 bytes for section size), rename to NDS.
3. It should default to song select 0x00 for most sets, if you want something else to play, change the two bytes at offset 0x0d0fc0 in the NDS file (of course, nongeneric drivers have the song select at different offset. Depacking mini2sf and checking the loading address should help). Valid values you can take either from a SMAP file (again, VGMToolbox can both extract the SDAT from the NDS file and generate SMAP from that) or by depacking the mini2sf files