Better, to Death:

For once, Death appeared not to smile.

He brought his hand down on the strings.

There was no sound.

There was, instead, a cessation of sound, the end of a noise which Susan realized she'd been hearing all along. All the time. All her life. A kind of sound you never notice until it stops . . .

The strings were still.

There are millions of chords. There are millions of numbers. And everyone forgets the one that is a zero. But without the zero, numbers are just arithmetic. Without the empty chord, music is just noise.

Death played the empty chord.

The beat slowed. And began to weaken. The universe spun on, every atom of it. But soon the whirling would end and the dancers would look around and wonder what to do next.

It's not time for THAT! Play something else!

--Soul Music, Terry Pratchett

Silence can be part of a piece of music (and that's been obvious since long before Cage; that's not the point he was making) but that doesn't mean silence is a musical chord.

Similarly, atheism is an opinion on a question relevant to religion but it isn't a religion.

A musical chord is defined as three or more notes played at the same time. I could see complaining about the definition being wrong if it was one or more notes, or even two or more notes, but when it's three or more notes I think it's clear that it means something more specific than a set of notes.