The story goes that the London musical crowd of 1567 was in a spin over Ecce beatam lucem, a choral work for 40 individual voices by Allessandro Striggio. At the time there was competition between English and Continental music publishers. The Duke of Norfolk issued a challenge to English musicians to better the Italian effort and the result was Spem in Alium by Thomas Tallis.
Another version says that Tallis wrote the 40 part motet for the 40th birthday of Queen Elizabeth I in 1573. The choice of text, from the Book of Judith, may have been to flatter the Queen, comparing her to the heroic Judith.
Whatever the truth, Spem is Alium is one of the treasures of Elizabethan English music. It is scored for 40 individual voices, divided into eight choirs of five voices each. The opening theme weaves its way through the eight choirs one by one, until all 40 voices come together in a climax at the 40th bar.
[Good Music Guide]
It is blow-your-socks-off good.
The Choir Of King's College, Cambridge (conductor: David Willcocks) - Tallis: 'Spem In Alium' (1965)