'Of the 80 students I've taught, only one other besides Rebecca has taken the test and that student passed,' said Mrs Tan Khe Tong, 81, who has guided Ms Koh for the past three years.
The test, which Ms Koh took a week ago, requires one to play five pieces, with some clocking in at 20 minutes.
So how does Ms Koh, 30, who was born blind, master music sans reading scores of some pieces which can run to 18 pages?
Said Mrs Tan: 'Her ears are her eyes. Her fingers give her the will to press the notes and her determination enables her to endure hours of practice.'
Said Ms Koh, an only child, who does not work: 'Since birth, I could only listen to the things around me, and in the end, I fell in love with music.'
Her father, Mr Sebastian Koh, recalled that when she was six, she could reproduce music he had taught her on the organ. 'I knew then that she was talented,' he said.
She started piano lessons at seven and completed her Grade 8 examination in 1998 at 19.
In 1999, however, the lessons were discontinued after her father's business of selling second-hand pianos failed.
Read the full story in today's edition of The Straits Times.