Layout userlist columns

I have been wrestling to get the layout of a userlist in the following format:


Trombone Horn

A s
b d
c g
d
f
g

Cornet

w
e
r
t
y
u
i
etc.

What I get is this:


trombone a
trombone b
trombone c
etc.

I need to have the instrumentnames as a heading with underneath the names of the musicians playing that instrument.
The table can go over to the width of the page or just 3 columns for instance.

Any suggestions how I can accomplish this?

Rgrds, Pieter