Code Geass R2 episode 7,there is a song playing at 6:40 In Code Geass season 2 episode 7, there is a song playing at 6:40.This is about the time when Lelouch breaks his phone and throws it away when Kallen calls him. I can't find the song in the OST and I'm pretty sure it has been featured elsewhere in the series as well.

EDIT: I also noticed it play in episode 8 at 12:27.Corrected season number.
Found a playlist on YouTube that includes all the tracks excluded from the OST.

The track you are looking for is "Path of Decisions". It is the 30th video in the playlist I mentioned before.