Yeah, but only the player has any concept of 'presets'. The DSP only has a concept of 20 bands of EQ. ie, we cannot tell the DSP to select preset X, we have to tell it each and every parameter.

Ummm... I wasn't going to get quite so sophisticated as to write to the DSP, I was kinda thinking along the lines of just injecting button codes to select EQ presets via the player menus. Selecting EQ's might take six or seven button codes max, and it might take the player all of one or two tenths of a second to make the change once the codes are received. To hide the ugliness of the menus coming up, I can hide the player's screen (by keeping a copy of the last player buffer before the change onscreen instead) so all the user will see is a fraction of a second of the screen freezing.

I'm already doing all this with visual changes (with very nice results so far.)