It really depends on the type of harp. Most are triangular shaped, but Celtic harps are more curved, almost like a mango shape.
Decagon
ambot lang?
A decagon.
ninagon
A hendecagon,
it is called a unbalnced shpe
A cone.
harp
A 27 sided shape is called a Icosikaiheptagon.
A pentagon
The Harp
A trapezium is not a regular shape although it is a 4 sided quadrilateral.