"The music is in your head," the light artist told AAP.
"For some people they're a jazz musician, other people are pretending they're Elton John."
The baby grand is just one of the items in O'Brien's Melbourne workshop, which is lit up with neon shapes such as mountains, butterflies, even a drum kit and mic setup.
When these instruments are installed at various events and festivals, even the least musical punters are inspired to have a go, explains O'Brien, thus becoming a part of the artworks themselves.
"Every person's experience with my art is completely unique ... that's the joy I get looking online and seeing people's photos."
Online images have been integral to her success - O'Brien visited the Burning Man festival in Nevada in 2009, and decided to become a large scale installation light artist.
Back in Australia, she taught herself how to construct in neon by watching YouTube videos and began making festival installations, including a pair of neon angel wings for Melbourne's White Night.
When she returned to Burning Man in 2016 with the wings, singer Katie Perry posted a photo of them on Instagram and O'Brien's artwork was seen by millions.
Despite the images going viral, O'Brien was running her neon venture from home until just on a year ago, with installations stored in warehouse B (the bathroom) and others in warehouse H (the hallway).
She has since moved to a South Melbourne warehouse where business has grown to five full-time staff.
Her installations are not made from glass neon but a newer product called LED neon flex, which is bendy and safe to touch.
They are part of a 10-day winter lights festival in Melbourne, Rialto Aglow, starting July 19.
O'Brien has taken her light installations around Australia and the world, and says Rialto Aglow is the first festival to take a specifically business district and light it up at night.
She also believes her neons are unique in the growing international market for public light art.
"It doesn't seem anyone else is creating ground level interactive light art that riffs off the everyday," she said.
Another new Melbourne festival, Now or Never, will run from August 17 to September 2.
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