Spellsong

Spellsong was the ability to invoke various magical effects through song and music.

Casters
Practitioners of the Spellsong were known as Spellsingers and were individuals who had the innate ability of using their voice to produce melodies with magical properties. Eventual training could only refine this ability. The process of using this art consisted of singing and dancing alone or with other spellsingers, usually around a focus or a creature intended to receive the effects of the magic.

Spellsingers often were female humans--the Chosen of Mystra--, elves, and half-elves, though exceptions abounded. The Sword Dancers (priestesses of Eilistraee, banished daughter of Corellon), for example, were an exception in that they also included female drow, skilled in the art of Spellsong and able use it to channel Eilistraee's magic to obtain the goddess' blessing. Similarly to how Bladesingers fought in combat, they had the ability to sing their magic even amidst the chaos of the battle, while dodging and dancing around, or while wounded, so long as they could intone their musical prayer to their goddess.

Effects
Together, spellsingers could use their art to work a variety of magical effects of immense power, but the song of a single caster was often not very powerful. Multiple spellsingers could dance and sing in coordination to perform rituals capable of working more powerful magic, like healing wounded or ill creatures located near the casters (albeit generally not with the same power of major healing spells), sending simple messages, visions or indications to individuals known to the majority of the casters, repelling undead or evil creatures and making magic items glow, activate or levitate.

Elves in particular had an innate inclination to spellsong--elven High Magic, for example, was, or could be, a form of spellsong. Before the Spellplague and their Retreat to Evermeet, elves used their cultural variation of spellsong, as bequeathed to them by the Power of the Seldarine, to raise cities from mountainsides, to invoke a mythal, or a gate (Tintageer), and to wreak unspeakable havoc (the Ever'Sakkatien; the Dark Disaster).

Particularly powerful spellsingers had the ability to use their song to call upon the Weave, invoking spells similar in power to those of a mid-level wizard or sorcerer. The Sword Dancers of Eilistraee were examples of this.