Key of Bartok's No. 5 from "Ten Easy Pieces"

[dorjuanhoop]

     Can someone explain what key Bartok's Evening in Transylvania" is in? 

[bernhard]

This is not a very useful way to analyse this piece.

Instead of thinking in which key it is, consider "key centres". If so, the key centres in this piece are E and A, mostly in the Aeolian mode. However, most of the melodic lines are pentatonic.

Now see if you can anlyse it.
(Get a bunch of coloured pencils and as you identify the patterns I pointed out, circle them and see how they relate).

Incidentally, this was one of Bartok´s favourite pieces and he often performed it.

Best wishes,
Bernhard.