The Symphony was created by the Choir, a group of plaguechanged creatures that sang a telepathic tune that could be heard at any point between Neverwinter, Helm's Hold, and Gauntlgrym. The song was powered by the Spellplague energies the aboleths harnessed from the Cauldron of Blue Fire. Therefore, those creatures chosen to be part of the Choir were subjected to a series of increasingly traumatic tests to determine their aptitude to "sing" in the Choir, and eventually were warped by the Spellplague energies into something unrecognizable.
The song of the Choir was, in essence, a beam of focused Spellplague energy that could twist stone or flesh depending on subtle variations in the Choir's harmony, warping reality in ways that made sense only to an aberrant mind. By using the Hex Locus, the Sovereignty could enhance the Symphony's range, to reach places far away from the normal range of the Symphony.
Those who "heard" the Symphony would suffer horrible nightmares. The only way to avoid having nightmares within the Symphony's range was to sleep near a dreamthief doll. Excessive exposure to the Symphony could turn creatures into spellscarred or even into plaguechanged beings. If focused against a creature or group of creatures, the Symphony could corrupt and twist the mind of the targets, turning them into thralls of the Sovereignty, puppets whose only purpose was to serve their masters to the best of their abilities, or even turn the most unfortunate targets into foulspawn if the corruption went too far.
The Symphony of Madness began to be sung some time after the Spellplague of 1385 DR had transported the Abolethic Sovereignty to Faerûn. Sensing the presence of Maegera, the aboleths wanted to use its power for their own ends.
The first tests of the Symphony occurred a few years later, when the Sovereignty used the Symphony to corrupt the elder brain of a colony of mind flayers living in Gauntlgrym, something that in turn corrupted the mind flayers, turning them into plaguechanged puppets of the Sovereignty.
- Matt Sernett, Erik Scott de Bie, Ari Marmell (August 2011). Neverwinter Campaign Setting. Edited by Tanis O'Connor. (Wizards of the Coast), pp. 91–92. ISBN 0-7869-5814-6.
- Matt Sernett, Erik Scott de Bie, Ari Marmell (August 2011). Neverwinter Campaign Setting. Edited by Tanis O'Connor. (Wizards of the Coast), p. 172. ISBN 0-7869-5814-6.
- Matt Sernett, Erik Scott de Bie, Ari Marmell (August 2011). Neverwinter Campaign Setting. Edited by Tanis O'Connor. (Wizards of the Coast), p. 129. ISBN 0-7869-5814-6.