In the original song, Leonard Cohen clearly laughs when singing about the monkey and the plywood violin. It can be heard here.
However, in live shows (e.g. in London) he's not laughing at that point in the song.
The only reference I've found online to the laughter is here:
The items are the monkey and the plywood violin. A monkey is what an organ-grinder needs (remember an organ-grinder isn't a proper musician, but simply turns a handle that makes the pianolla play); a plywood violin is a toy. Thus, the items that have been sent to the singer are thinly-veiled insults (hence the hollow laugh)...
Which makes total sense, but this does not explain why in the live show he's not laughing. Can anyone find any explanation to this? Or think of a good reason?