Choral Public Domain Library

Secondly: excelsis. As 'eks-chelsis' is quite a mouthful, many are prepared to compromise by singing 'ek-shelsis', which calls for less movement of the tongue and sounds fairly similar. There's more to it than that: this is actually the pronunciation recommended by the Solesmes monks for Gregorian ...

The Latin looks a bit odd, especially the 'O' followed by an accusative case. I would have expected 'O vir ineffabilis', but my Latin is quite rusty. So is mine, but a bit of Googling led me to references to an 'accusative of exclamation', the most famous example being Cicero's 'O tempora, o mores'...