A mutation stop of 1-1/7' pitch in the manual, or 2-2/7' in the pedal. According to Grove, it was first known as an idea in Prussia around 1780, and the name Septième was introduced by Cavaillé-Coll. It was that builder who first brought it to prominence in France in the 1860's. Harrison & Harrison was the first English builder to use it extensively. Wedgwood writes:

The Flat Septime was introduced by Mr. Jackson, of Liverpool, by whose son it was fortuitously discovered one day in 1874 [sic; 1847?], when tuning “close,” at the voicing machine, the chord of C, E, G and minor 7th. He was surprised to hear, as soon as the last note became perfect, a deep note like that of a reed, an effect due, of course, to the production of a powerful resultant tone. In 1848, the Flat Septime was inserted at St. Mary, Bootle, near Liverpool, and at Whitworth Parish Church, and in 1849 on both manual and pedal at Liverpool College.

The name Sharp Twentieth is extremely rare, and a misnomer. See Twenty-Eighth, Flatted.

Examples

Osiris contains about fifty examples each of Septième and Septime, and two examples of Twenty-First. No examples of the other names are known. Contributions welcome.

Twenty-First 1-1/7', Swell; Irvine Auditorium, Philadelphia, Pennsylvania, USA; Austin 1926.

Twenty-First 1-1/7', Choir-Swell, Great-Solo; Twenty First 2-2/7', Pedal; Convention Hall, Atlantic City, New Jersey, USA; Midmer-Losh.

Septime 2-2/7', Hauptwerk; Septime 4-4/7', Pedal; Dreifaltigkeitskirche, Liepaja/Libau (Lettland), Latvia; Grüneberg 1885.

Bibliography