Mighty organ, many-piped

The phrase "mighty organ, many-piped" appears in quotation marks in Max Beerborm's Zuleika Dobson (chapter 2, on p. 19 of my 1952 Penguin edition). Does anyone have an idea of its source?

I've read Zuleika Dobson, but I don't remember that quote, nor do I have a copy handy. I think we need a couple of sentences more just to understand why he says it. The actual phrase doesn't sound particularly distinctive. All mighty organs are many-piped. Even ordinary ones are many-piped; it's an instrument made up mostly of pipes.
SS