Someone has probably done this already, but it turns out that you can use ResEdit to extract the assembly source code for the DSP Linker's various built-in effects. I'm not entirely sure how much of it works or translates into the DSP's machine code (and some parts have seemingly-obfuscated variable names like _GFGLBf100), but it could be a useful reference for understanding the typical 'look' of a DSP program or adding your own modifications to the effects.