I'd be interested to know what the new chunks are used for. The style file is a specialized MIDI file. I know OTS and CASM are non MIDI chunks in the style file that tell which Right hand Voices are used and how the style will play respectively, but what has been added since the SFF GE was implemented? PJ, you say the new style chunks will hold the "adaptive stuff" and will be ignored by older keyboards... so what's up? Is this related the MIDI 2.0?
Joe's description and examples are basically correct. A style file -- which is a container holding a bunch of bytes -- is separated into compartments called "chunks". A chunk is merely a group of bytes. The first few bytes identify the type of chunk.
So, there is a MIDI chunk, an OTS chunk, and a CASM chunk. Nothing new. Also not new -- and you may never have realized it -- is a "CdS1" chunk which holds unexpanded chord information.
Audio styles have their own proprietary chunk(s). Adaptive styles have their own proprietary chunk.
As far as normal people are concerned, you can and should ignore the existence of chunks. If you are interested in creating your own styles from scratch -- or build the software tools to make styles -- then you need to know about chunks.
Basically, big new features like adaptive or audio need their own data. By putting them into feature-specific chunks -- which can be ignored by old software -- Yamaha avoids file format versioning which would drive normal people right up the wall. You think SFF1 vs. SFF2 is bad? Try choosing the right version among 1.1, 1.2, 1.3 ad infinitum. Gaaaaaaaaaaaaaaa!
This is way too much information for most people -- only style nerds.
-- pj