thats looks fun 
listing says SED = Spectral Energy Distribution
I was going to say perhaps a filterbank, but given its only one knob… perhaps something like bandpass filter? (hence also resonance control)
that said a bandpass filter, might be a bit ‘underselling it’, might be a number of filters that are linked…
so as to model a specific kind of resonator to mimic a trumpet.
does really matter , as long as it sounds good - which is does.