MIDI and instrumentEqualizer

[Nicolas Kielbasiewicz]

Hello !

I would like to have more information on instrumentEqualizer.

I have currently a StaffGroup with 2 Staves and a ChordName.
Each one has its own midi instrument and I would like to set the volume 
of each instrument. As I don't want to modify the midi.scm, because I 
want to set the volume each time I have a score, it seems that I have 
to use instrumentEqualizer, but I didn't find the syntax.

In advance, thank you

Nicolas