Me again, Mousethief,

Just checked AMG - all music guide (www.allmusic.com)and this is part of what they say of Zeppelin.

"They rarely gave interviews, since the music press detested the band. Consequently, the only connection the audience had with the band was through the records and the concerts. More than any other band, Led Zeppelin established the concept of album-oriented rock, refusing to release popular songs from their albums as singles. In doing so, they established the dominant format for heavy metal, as well as the genre's actual sound."

which is consistant with what I remember (up to the mid '70s)

Rana