The Three Rivers Music Society (popularly known as TRMS), a registered charity, was established in 1975 with the object "to promote, improve, develop and maintain public education in and appreciation of the art and science of music in all its aspects by the presentation of public concerts and recitals and by such other ways as the Society through its Committee shall determine from time to time."
This it does primarily through an annual programme of six evening and four lunchtime chamber concerts at local venues. There is also a friends' social evening and a fund-raising supper evening each year, both with musical entertainment provided. In association with the Rotary Club of Rickmansworth, TRMS sponsors the Rickmansworth Young Musician of the Year competition which culminates at a concert in July when the Young Musician of the Year is chosen. Following the TRMS Annual General Meeting, held each September, finalists from the Rickmansworth Young Musician of the Year give an informal recital for members.