About how to sing choral works:

“The first thing is the character. Then comes nothing, then the notes, and then everything else.”
“It's better to be bad than to be boring.”

And later:
“Psyche is the first in life. All else comes from that.”

And later still:
“If you're not an actor you cannot make music.”
“How you say it is more important that what you say.”
“Live your emotions and feel them; that's the most important thing.”
“What is your aim in this piece? In everything in life, you must have an aim.”

About flow and phrasing:

“Don't go on swimming in the lake, but turn to the river.”

About singing loud and soft:

“If you're only soft, then you cannot be soft.”

And later:
“A man who's only strong is never strong…because he is sick.”
[Or equivalently: “If you're only loud, then you cannot be loud.”]

About singing (in the Haydn mass) “Et expecto, et expecto”:

“Think about what it means to repeat something when you're speaking,
as in: ‘Give me a beer...GIVE ME A BEER!!!’”

And later:
“Say something the second time for emphasis”.
“I live on exaggerations.”

About singing “mor-to-o-rum” after “re-sur-rec-ti-o-nem”:

“Dead people have another color of singing.”

To sopranos singing a final ppp “Je-sum Chri-stum” in a Bruckner motet:

“They have no bodies, so they cannot have vibrato.”

About conductors:

“Conductors hear much less than you think, but they see much more than you think.”
And later:
“We cannot replace conductors by computers. I am not a policeman; I am not a metronome.”