The 13th note is a powerful magical note which exists in the show's universe. The note can only be played by a handful of people, known as Sonic Warriors, who can use the power to create shields, cages or bolts of light that can be used to attack objects, shields and people. A battle like this is called a Sound Clash
There are a number of sonic lords, like Sugar Che, who are powerful beings who protect the sonic power and who seem to be ageless; living for hundreds to years. Sugar recruited the band Freefonix (BB, Freezbone and Mostart) to fight and protect the power of the 13th note.
The 13th note can be used for evil purposes, mainly by the show's main villain Vox, who is an evil sonic lord that some time ago tried to take over the world and was stopped and locked away in a sonic prison called The Void of Silencia by Sugar Che. A blast of 13th note energy could free Vox and allow him to escape to earth. Working for Vox are Freewave band, Mantyz who have a corrupted thirteenth note power, and who regularly battle Freefonix. Vox materializes in a mirror in the office of Mya at ComaCo. Mya has been tricked to believe that if she helps Vox, she will get endless riches and power. Likewise Mantyz were tricked into the same thing by Mya when she gave them a record contract.