9 .
There was a healthy tradition of polyphony (singing in parts) and antiphony (singers, or sub-groups, singing 'against' one another across a large space such as the interior of a major church or cathedral) by the Tudors ~ say, four or even five centuries ago. Like any other technique (such as organ-building), there would always be the implicit challenge to 'go one bigger', even, than the vocal and brass choirs of that golden age in Venice.
Thomas Tallis (1505 - 85) famously made a setting of the liturgical text Spem in alium nunquam habui ... for how many voices?
36 singers divided into 6 choirs
40 singers, as 8 choirs of 5 parts each
48 singers ( = 8 x 6-part semi-choruses)
60 singers ( = 1 5-part choir to represent each of the 12 Apostles, or Tribes of Israel)
Gerard Hoffnung, the emigre musician, cartoonist and absurdist, arranged a series of 'Hoffnung Music Festivals' in the straiter-laced days of the 1950s, during one of which a 'great living composer' was to come onstage and direct a top London choir in an excerpt from his latest groundbreaking work. Whatever the audience might or might not have been expecting, it probably wasn't this single shouted word, entirely shorn of its dramatic context!