Iranianradio.com (you can stream it from iTunes) provides some of the best concentration aid I've found for writing.
On the right kind of day, Bulleit is also good.
So is a clean apartment.

Gerald Stern makes me so happy. I want to write rip-roaring grief poem the way he does in the example I'm about to quote. I want to have the rights to that kind of sorrow.

...I'm kissing Stieglitz

goodbye, my arms are wrapped around him, his photos
are making me cry; we're walking down Fifth Avenue;
we're looking for a pencil; there is a girl
standing against the wall—I'm shaking now

when I think of her; there are two buildings, one
is in blackness, there is a dying poplar;
there is a light on the meadow; there is a man
on a sagging porch. I would have believed in everything.

- Gerald Stern, Kissing Stieglitz Good-Bye