It would appear that Milton's suggesting that it's chastity that actually establishes something like a precondition for hearing and learning that inspired song that's actually sung before the throne of God in Revelation.

那表明了弥尔顿的建议,关于确实是贞操建立了某些事物,像听和学的事先准备对歌的启发作用,在《启示录》里确实在上帝面前唱了。

耶鲁公开课 - 弥尔顿课程节选