I think Hoffnung's stuff is still held actively in copyright - I have seen books and recordings - I even managed to score some (if not all) of the animated toons on a DVD of collected animations.

Quite a lot of these have been turning up in Aus in the 'cheapies' - I sat down and hand indexed them ...

On 101 Cartoons - Aussies will understand when I say - available in Crazy Clark's for AUD$30 - if they have any left.

Hoffnung Music Academy
Hoffnung Symphony Orchestra
Hoffnung Vacuum Cleaner
Professor Ya-ya's Memoirs