Piano was introduced by Gulbransen and was considered very good. Compared to today's advanced sample voices it would be considered primitive. It was generally best used for a single lead note melody. Wasn't as convincing with chords unless they were played in an appegio style. I've not used the piano feature much on my Thomas or Conn organs, but did use it on my Hammond Colonnade, especially on the lower manual where it had an automatic appegiator. It added nice variation to novelty sounds and pop songs.