A 042

Snowsong is an Area spell, and follows the general rules for such spells.
Regardless of the shape of the area, you select the point where the spell originates, but otherwise you don’t control which creatures or objects the spell affects. The point of origin of a spell is always a grid intersection.
An Area spell can move with the caster, but that needs to be explicitly stated. For example:
Quote Originally Posted by Antimagic Field
An invisible barrier surrounds you and moves with you.
The Snowsong description contains no statement about it moving with the spellcaster. Consequently, Snowsong is centered on a grid intersection that was part of the spellcaster's square(s) at the time of casting, but does not move thereafter.