Yep. It's part of the surname: "van Beethoven". It's silly how different names work from country to country. Icelanders use the patronyms for surnames. In Denmark you have two surnames, one of which is called a middle name, but both are inherited rather than given. In Netherlands the "van" and "den" and "op het" and so on are called "tussenvoegsels", "between-additions", furthermore outside the home in writing mostly only the initials of the given names are used. And this is just a tiny part of Europe, conventions are even more diverse in other places. For instance the common American custom of having a middle initial is strange to me.
Thanks - I've amended the clue. I made the mistake, because no one really every says "van Beethoven" when talking about him: they just say "Beethoven". So the 'van', while in reality part of his last name, kind of functions as a middle word only ever said in the context of his full name. I stand corrected though!
A while ago my wife suggested a 'First name of Composers' quiz and mentioned Beethoven etc. I said that the first comment would be 'van' Beethoven and should it be there or not etc.etc ................. I was right!
Couldn't think of Holst's name- got the rest. Haydn's first name is actually Franz...then Joseph, but it's easy enough to figure out what to type in for a hit... Enjoyed the quiz!