The Flute-Blade of Mato Grosso is a magical ceremonial blade, worn as a symbol of office by the current Protector of Bluemoat, the keep which serves as capital and seat of authority in the Mato Grosso region. The sword magically changes its shape and size to appropriately represent its wielder, though some characteristics are consistent with every change. The Flute-Blade always has a crosspiece of some kind, and only ever has a single edge.
That crossguard and the rear, blunt edge give the the blade its unusual name. An aperture for air to pass through in the crossguard, as well as a number of holes running down the blunt edge of the weapon, allow for its wielder to utilize the sword as a musical instrument when the sword is exposed to the magically-charged winds of Fantasia.
Bluemoat’s highest parapet is always swirling with such winds, and from that vantage point the Protector uses it to play well-known standards at various times of day, such as Reveille, Matins, and so on. However, wielders are often known to compose their own pieces with specific meanings and styles that match their own character; many of these pieces remain famous and popular long after their composers have stepped down from their role as Protector.
In the case that the Protector needs to sound a call, but does not have access to a magically charged wind, it is possible for them to expend some of their own magical life energy (as denizens of Fantasia) to play the Flute-Blade, though it will likely be far less powerfully audible, and comes at no small expense to their reserve of internal manna. Al-Suyá’s thoughtful but inspiring compositions are still well-known among the denizens of Bluemoat, and would likely elicit a response from those still loyal to him, even if played on an instrument other than the sword itself. What songs can be expected from the newest wielder, La Shushu, is anyone’s guess.