He's been an organist for many years and he has a rather large pipe organ installed in his house, he even travelled to Europe to visit some organ makers before

He's been an organist for many years and he has a rather large pipe organ installed in his house, he even travelled to Europe to visit some organ makers before setting on an American organ maker. If you search "Knuth organ" on Youtube, you can find various interviews where he talks about it. You can see the specs of the organ here: https://www-cs-faculty.stanford.edu/~knuth/organ.html https://www-cs-faculty.stanford.edu/~knuth/organ.html