Ong Gim Dee burst onto the local music scene as a harmonicist with his debut performance at Victoria Concert Hall in 1985. In the following years, he continued to perform at concerts and events variously organised by the Ministry of Cultural Development and the Radio Station. After a few years of hiatus, 2008 saw his triumphant return to the stage with performances across Singapore, Hong Kong, and China. Since 2010, he has been acting as a judge at the annual Asia Pacific Harmonica Competition. His passion for the harmonica began at a very young age. As a student, he spent his days practising for and performing at school concerts and festivals. In his later years, he apprenticed under Mr. Soon John Kwang, and Mr. Ho Chong Wing, himself a protege of the famous harmonicist Tommy Reilly. He has continued to reach new heights under the tutelage of Mr. Joe Sakimoto, the pride of Japan, and Norway's celebrated harmonica master, Mr. Sigmund Groven. He has also contributed to the growth of the local music scene in many other capacities. In 2019, he worked with the Harmonica Aficionados Society and Hohner to organise a concert at the Esplanade featuring Mr. Sigmund Groven. He is currently hard at work increasing the presence of the harmonica within the local music scene.