a lot of people just seem to be using ARM Cortex-M processors instead of DSPs these days. but i doubt most of them are doing all that much with them. the DSP chips in keyboards like Nord Stage are quite beefy in comparison. sure, for stuff like guitar pedals, you can get away with the modest performance of a Cortex-M4. your average guitar pedal is just a simple filter chain on a low-bandwidth signal. but i think having a dedicated DSP chip is justified for the project i'm working on.