Heres the low down, if you dont know already.
Pull up the macro screen.
Name of Macro (your choice)
(type) /melody (here is the spell jem number) 1-8 (# space # space# space #)
example. /melody 5 7 3 8 1 (this will play the songs in the spell gems 5 7 3 8 1 in that order repeatedly.)
accept the set up and move the macro to your hotbuttons.
Now if you chose songs that use instruments set up you Bandoleers. (B or shift B will bring up the bandoleer window)
In your primary have a weapon. In the secondary put an insturment. Name the Bandoleer after the instrument. click add and move to hot buttons.
do this for as many bandoleer slots you wish to use.
Now when you play the melody all you have to do is hit the hotbutton for the bandoleer instrument congurient with the song in the melody. do this in the last 1/5 bar of the current song in the melody and you will maximise the song effect without useing up all the time with one wep and instruent.
If you dont understand this, i think you'll figure it all out in 15 levels anyway.