The function static s32 SEQ_MIDI_IN_Receive_ExtCtrlCC(u8 cc, u8 value) need to be modified like this static s32 SEQ_MIDI_IN_Receive_ExtCtrlCC(u8 cc, u8 channel, u8 value)
Well, i would like to add an option in the external control list Mutes By Midi Channel, where you select a CC , and each channel of this cc will mute/unmute one track: ex CC122 ch1 mute track 1, CC122 chl 2 mute track 2, etc…
Do you have experience in programming? The reason I ask is because it requires that. And your approach of changing the args of a core function is definitely not the right way.
Btw: I think this is pretty custom for your needs, since the mute works in a different way in the midi implementation (regarding tracks).
Otherwise, if you absolutely need it and above all if you are confident that you can do it, then you can hack the seqv4 source and define and include your own external control as a CC and specify & transmit the channel there as a value, which is used in your own loop through the tracks and mutes or unmutes the corresponding tracks if (value == track’s channel).