MidiControl is sending midi Continuous Controller data to a VST instrument or external hardware synth.

This instrument is meant to be used together with another instrument that produces the notes. This other midi instrument migth be as simple as:
midion p1, p4 , p5 ;channel, number of note, velocity of note
Both instruments (the note producer and midiControl) must run in parallel, using the same midi channel.

with MidiControl, you can assign for example the brightness, volume, panning etc. etc. to one of the faders and draw the Automation Lines.

The speed of midi transfer is 31,25 kbit/s = 31250 bits per second. If the ksmps of Csound is too small and thus the speed transfer of the midi data > 31250, the hardware synthesizer might get too crowded and the midi buffer of the synth full. This may lead to midi information being skipped or even - on older synths - cause the synth to "hang".
With the setksmps opcode set to the right speed i suspect this cluttering will be avoided.

version 1.1, november 2017
- cooler and more clear GUI

version 1, november 2017
- needs Blue >= 2.7.2