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“dsp” files are IFF files (Interchange File Format) which store the DSP program and metadata.

IFF files are made up of “chunks.” A chunk is made up of an id (4 chars), size (32bit signed int), and data (byte array). In C/C++ a chunk structure would look like this:

typedef char iff_id_t[4];

typedef struct iff_chunk_s iff_chunk_t;
struct iff_chunk_s
{
  iff_id_t id;
  int32_t  size;
  uint8_t  data[0];
};

Syntax definitions from the original IFF document:

Chunk    ::= ID #{ UBYTE* } [0]

Property    ::= Chunk

FORM    ::= "FORM" #{ FormType (LocalChunk | FORM | LIST | CAT)* }
FormType    ::= ID
LocalChunk    ::= Property | Chunk

CAT    ::= "CAT " #{ ContentsType (FORM | LIST | CAT)* }
ContentsType    ::= ID    -- a hint or an "abstract data type" ID

LIST    ::= "LIST" #{ ContentsType PROP* (FORM | LIST | CAT)* }
PROP    ::= "PROP" #{ FormType Property* }

In this extended regular expression notation, the token "#" represents
a ckSize LONG count of the following {braced} data bytes. Literal
items are shown in "quotes", [square bracketed items] are optional,
and "*" means 0 or more instances. A sometimes-needed pad byte is
shown as "[0]".

More information:

• https://en.wikipedia.org/wiki/Interchange_File_Format
• http://www.martinreddy.net/gfx/2d/IFF.txt (local copy )

Details in part taken from the SDK documentation.