A while ago I got an STM32F746 to do some DSP with it, and it looks like a decent all-in-one board to implement audio dsp algorithms.
Unfortunately I had some issues with it, like accessing buffers in sdram and saving data using sections.
As I mentioned on the official STM32 forum (https://community.st.com/message/176518-stm32f746-for-dsp-audio-effects (https://community.st.com/message/176518-stm32f746-for-dsp-audio-effects)), one bug is in the delay buffer: it should iterate AUDIO_BLOCK_LENGTH samples, but iterating more than AUDIO_BLOCK_LENGTH/2 samples results in noise.
Lately I haven't done much with it, so I published the draft project, with a tremolo, stereo delay and basic UI, on github, if someone wants to give it a try and share ideas.
Project https://github.com/freakk82/STM32F746_DSP (https://github.com/freakk82/STM32F746_DSP)