Their best friends and they know what to do and where to go.
Sometimes they play together but sometimes they sleep together.
Here is their story...

Ponyville is full of music that can be heard everyday and everynight but all Octavia's songs are now unpopular so she go through whole Ponyville to inspire herself and then write a song or just a melody.

Indigo Zap and Sunny Flare are best friends.
But they never go out from home so one day Indigo decide to go to the forest but she wanted Sunny to go with her...

Cover art: http://a-kwiatkowski.deviantart.com/art/Dark-forest-342663014
I added Sad tag because some moments are sad.
Large part of the story is not in the forest - Part in forest is in Chapter 1