Elven Chorus

Elven Chorus doesn't change when you can cast creature spells. Normally, this means during your main phase when the stack is empty, although flash may change this.

You can look at the top card of your library whenever you want (with one restriction; see below), even if you don't have priority. This action doesn't use the stack. Knowing what that card is becomes part of the information you have access to, just like you can look at the cards in your hand.

You'll still pay all costs for the spell, including additional costs. You may also pay alternative costs if any are available.