how long...in the nothingness of NOW....how long...how long...

 "40", also known as "40 (How Long)", is a song by Irish rock band U2. It is the tenth and final track on their 1983 album, War. The song is noted for its live performances; guitarist the Edge and bassist Adam Clayton trade instruments during performances of it, and as it was commonly played to end their concerts, the band would leave the stage one-by-one as the audience continued to sing the refrain ...

"How long to sing this song?"

..... Psalm 40.

How long to sing this song
How long to sing this song
How long, how long, how long
How long, to sing this song

He set my feet upon a rock
And made my footsteps firm
Many will see
Many will see and fear

We wrote this song in about ten minutes, we recorded it in about ten minutes, we mixed it in about ten minutes and we played it, then, for another ten minutes and that's nothing to do with why it's called '40'.