"There was a lot of wasted space. It needed to be redesigned."
It now has a dance floor, five practice rooms, a keyboard/computer room and a classroom, all soundproof, while double-glazed windows offer views to Cape Kidnappers.
There is purpose-built storage for instruments, music and resources.
"I gave the architect a list of what I wanted, and I got just about everything on the list, which is amazing," Ms Purdy said.
"I'm really lucky, as head of department, to have designed my own place and to be able to work in it. That's a bit of a dream, really.
"The students come in and their faces light up. The whole feel is light, bright and inspiring."