The Royal College of Organists (RCO) will perform a complete version of "Orgelbuchlein – Little Organ Book," a mysteriously unfinished organ work by German composer Johann Sebastian Bach in London.

The premiere of "Bach And Friends: The Orgelbuchlein Completed" will take place in September and demonstrate 118 new pieces of music composed to complete the unfinished "Orgelbuchlein."

German composer Bach intended for the original manuscript to contain 164 chorales but ultimately left it unfinished, with only 46 completed and nothing but the titles written for the remainder.

Over the course of more than a decade, the Orgelbuchlein project's director and organist William Whitehead has commissioned contemporary composers such as John Rutter, Judith Bingham, Sir Stephen Hough, Sally Beamish, Louis Andriessen, Daniel Kidane, Roxanna Panufnik and Nico Muhly to fill in the Orgelbuchlein's missing pieces.

The result of Whitehead and the composers' work is a new and now-complete "Orgelbuchlein," a collection of 164 short chorale preludes containing a cross-section of contemporary European styles, with newly edited versions of Bach's original pieces.

Speaking about the project, Whitehead said: "The manuscript of 'Orgelbuchlein' has always been such a tantalizing mystery, with no one knowing exactly why Bach completed only a quarter of his intended 164 chorale preludes.

"But by leaving the titles for the missing 118 pieces, he presented us with a unique and intriguing opportunity - what would happen if we commissioned the most interesting composers working today to meet this challenge in ways that reinvent the techniques laid down by Bach in ways which are entirely their own?

"The result is an astonishing completed work, an eclectic but cohesive whole with many of the schools of contemporary composition represented - minimalism, spirituality, new complexity, modernism, serialism and jazz, together with a range of styles from periods since Bach's death."

In addition to the 118 composers commissioned to work on the project, several individual sponsors supported the commissions.

Regional director of the Royal College of Organists and one of the organists performing at the event, Tom Bell, added: "The 'crowdfunded' nature of this project really is a remarkable feature.

"Through composition competitions and direct sponsorship, the RCO is delighted to have supported the commissioning of seven pieces, and other organizations have made major contributions, but more than half of those supporting this fantastic work have been private individuals - people from every walk of life who have been as captivated and inspired by this challenge as we have.

"It is an exceptional collective and collaborative artistic effort of which everyone involved should be immensely proud."

Among the musicians joining the eight organists will be the choirs of St. James's Palace Chapel Royal, St. Paul's Cathedral, and the Fred Thomas Trio.

"Bach and Friends: The Orgelbuchlein Completed" will consist of 10 events, running at various venues, including St. Paul's Cathedral, Westminster Abbey and Temple Church in the City of London from Sept. 23 to 25.

Each concert will be presented by broadcaster Zeb Soanes and feature a themed collection of contemporary pieces plus a selection of Bach's original compositions.

All performances of "Bach And Friends: The Orgelbuchlein Completed" will be free to attend with no pre-booking required.