Here are two documents about the mellotron, the instrument [almost]all proglovers like : both are short ( 2:20) and from Japan, the first is subtitled in Japanese and shows an overview of the inside of the "beast", sounds appears from 1:20 onwards; the seocnd show a tape replacement with japanese comments only ( no english caption).
http://www.youtube.com/watch?v=IKLWX_WLsTA
http://www.youtube.com/watch?v=eR6D1ZH2CMk
mellotronically yours
Mailo