The trio had been tutored by WYM conductor Atsuko Fukuoka and musician Ngaruaroha Martin.
At least eight other groups would also take the stage during the evening of music, she said.
"It's to welcome people into the space and it'll be a fairly informal concert ... It's from beginner through to the full orchestra," Ms Christian said.
The Whangarei District Council-owned Old Library had been shut for more than a year while administration issues were worked through and maintenance was undertaken to bring the 80-year-old building up to scratch for its new tenant.
"It's good, in a good central location. We're just working through a few details of sounds travelling between spaces," Ms Christian said. "Generally, it's going really well."
WYM's concert is from 5.30pm on Friday, at the Old Library. Free entry, koha appreciated.