You want to use a plain ol' horn. And you will miss MANY notes at first. I
would suggest going someone far away from people, kicking the song up, and
let it sit for a couple hours. That will give you a good start into the
skill. And contrary to what some people say, you do not have to have a target
for the skill to rise.
The place I chose for my AFK practice was in Qeynos Hills all the way across
the zone from the entrance to the karana's, up on the hill. I didn't see one
living thing and even after letting it sit all night I was still alive :)
Anyways, good luck to ya.

Renaldo Rallentando of the 34th String