Analysis of The Piano-Organ

My student-lamp is lighted,
The books and papers are spread;
A sound comes floating upwards,
Chasing the thoughts from my head.

I open the garret window,
Let the music in and the moon;
See the woman grin for coppers,
While the man grinds out the tune.

Grind me a dirge or a requiem,
Or a funeral-march sad and slow,
But not, O not, that waltz tune
I heard so long ago.

I stand upright by the window,
The moonlight streams in wan:--
O God! with its changeless rise and fall
The tune twirls on and on.