The Greater Kansas City Chapter of the American Guild of Organists will hold its 27th annual Bachathon, a celebration of the music of Johann Sebastian Bach, from 2 p.m. to 7 p.m. today at Grace and Holy Trinity Cathedral, 13th and Broadway, Kansas City, Mo.

The emphasis of this year’s program is singing. Every hour of the event will include either ensemble singing or audience singing.

The day will open with Bach’s “Magnificat,” BWV 243, performed by the Kansas University Chamber Choir, in their Bachathon debut under the direction of John Paul Johnson. Their performance will be followed immediately by a series of Bach chorales, sung by the audience and accompanied by area Lutheran organists: Rick Deasley of Atonement Lutheran Church, William T. Stewart of Immanuel Lutheran Church, and O. Wayne Smith of Faith Lutheran church.

Admission is free and open to the public, though an offering will be taken to help the guild continue free, public programming. Light refreshments will be provided at a modest cost.