You can set the various properties of a DSP (depending on the type) using:
DSP::setParameterFloat
DSP::setParameterInt
DSP::setParameterBool
DSP::setParameterData
The built in DSP’s have enum’s available for their properties to make things a bit easier:
https://fmod.com/resources/documentation-api?page=content/generated/FMOD_DSP_MULTIBAND_EQ.html#/
Our DSP Plugin API docs do have some info on this topic, under ‘Plug-in Parameters’:
https://fmod.com/resources/documentation-api?page=content/generated/overview/plugin_api_dsp.html#/