How to add a channel selection (solo) filter to ml_synth_basic_example

[AtmosphEng]

Hi Marcel and community, I currently have the ml_synth_basic_example working fine on an esp32 and a esp32-s3 board. Currently, when I feed a midi serial stream as input with multiple channel notes present they are all synthesized and are heard correctly. Now I would like to add a change with a new hardware control, something like a hexadecimal selection switch. The MCU could then read this switch as a chosen channel number and the software change would act like a filter, so that only the selected channel would be synthesized and heard i.e. like a solo, all other channels would be muted. The channel selection switch could be sampled periodically so that if the channel switch is changed during run-time then the the newly selected channel number would subsequently be synthesized and heard.
I don't know how to best implement this change (such a channel filter may even be already available in the code base) so could you please reply with some brief outline pointers as to how I can sensibly make this change with the existing code base. Thank you.