First magic primarily based on Music Glyphs, it's the partial success of Great Plague.
Music sheets imbued in the Circle of Fifths as magic runes with a Magical Catalyst in the center, lower versions use Aetherlight or Lunehymn, more permanent uses usually rely on a Mirrorbox Trap, a Resonance Box or Sky Glass. They appear through the Glyphic Heptastave and encode magic into the universal language of Spellweaving through music.
It requires Resonance and Stable Harmonic Channels to begin functioning. The music sheet is a Resonance Field dormant on potential acoustic energy that inscribes itself with Coherence through Sympathetic Vibration.
Music Glyphs work like Sky Glass that retains over a sigil a music track that needs to first store music to then play it back, they are like disposable disks where only the person that has the sigil can hear the music, it's useful for stealth as it is music that doesn't require playing sound. It's the primary vector in how assassins use Feather Fall Arts without having to play an instrument. They do, however, require to be in sync with the music they are hearing. This becomes a primary point in the Amadea, Sonata of the Violet Empress for Amadea.