Proto-Prog is a tag originated by the record dealers in the mid-Seventies. They put on their mailing lists once again the heavy-rock albums from the late 60s /early 70s, that were "proggy" & Hammond organ driven, and tagged them as *Proto-Prog*; thus, the term implies the heavy-rock albums like In Rock by Deep Purple, ...Very 'Eavy Very 'Umble... by Uriah Heep, As Your Mind Flies by Rare Bird and so on. Proto-Prog is a heavy-rock that features Hammond organ as a general rule, i.e. if an album doesn't feature Hammond organ and / or feature a synthesizer, it's not Proto-Prog. I'd like to start with this This thread is inspired by Listenin' to Prog and Conversation the thread.