The following information is from the Adventure Timecomic book series. It may not be part of the same canon or continuity as the animated series.
Acoustics Princess was briefly mentioned in Adventure Time Issue 5. She told Finn that if he were to sing loud enough at the correct frequency, he could shatter any pot. This helped him free Lamprey Princess from a pot without stepping out of line. It is unkown when she told him how to do this or why. It is also unknown what she looks like or where she lives.