How to apply an implemented effect to a midi and no midi instrument?

Hi,

1) I have a midi keyboard.

How, from an effect implemented in Command Window of Matlab thanks to an effect.m file, apply it (not to an input signal in Command Window) to a note of a midi instrument?

Which module(s) toolbox do you need to do this?

2) I have electric guitar no midi

Same question where the effect is applied to a rubbed string?

thanks