I apologize for my late reply.
These keyboards, especially the keys feel (due to the fact that they where made of wood and not such well-known plastic ones) close to a mechanical organ. Furthermore I can adjust the release of every single note with millimetre-level accuracy. Originally they were electronic action.
Meanwhile I always use the hifi-system and relinquish headphones
It sounds very realistic.
By the way - does somebody use the HOLZHEY (prospectum)? I love it...