I am the trombone

I am the trombone.

You are trying to make a sound.
You are trying to join the music around us.
But I am heavy. You cannot hold me up.
The conudctor uses his foot to push me into position.

You can see the music, but you cannot hear my sound.
I can't hear my own sound above the din of music around us.
Have I made a sound?

Though we try with all our might, no sound comes out.
Why do I have a mute in my bell?

You move my slide, but nothing changes.
What's wrong?

Why can't I sing?