Sister Composer

All that is known about Sister Composer is that she wrote the spell scroll that provided Aminah (one of The Hags) with the magic to animate the Gargantuan, Armored, Sentient Pumpkin

She also wrote this letter to Aminah,

The Letter

Sister,
Enclosed with this letter is the spell scroll for the Awaken Spell. The spell is written as a song, of course, and the lyrics are laughably false. They were necessary to secure funding for this scroll and many more like it. Ignore the meaning of the lyrics but not the lyrics themselves. The cadence, tone and breadth of your voice while you read the scroll are necessary pieces of a successful casting. This is a special inception of the spell, devised by Maester Irridain himself. It is specifically written to affect creations like that of Brother Creator and you do not need to even touch it to awaken it. However, it will not be charmed by you in the slightest. Better, the spell will incite it with fear and rage. No one will be able to convince it to stop, so wait until the moment is right. It may take a day or two for the rage to properly set in. May the Serpents guide your way, sister.

[The note goes on to describe various musical techniques and how to practice them before attempting the spell scroll]

Sister Composer

P.S. I know Maester Irridain sent you to Talon Pass for incompetence. Don’t be a fool and leave this note (or any other correspondence) where anybody can find it.
P.P.S. Please at least have the wit to trap this letter from any hand but your own.

Sister Composer

Delecanth Spibb Spibb