 The duos merged and became The Mystic Four, with Cees and Piet Veerman on vocals and guitar, Schilder on guitar (and piano), and Muhren on bass.By 1965 they changed their name to The Blue Cats, a reference to the colour of their suits and Cees' nickname, Poes (Dutch for 'cat').Dropping the 'Blue' from their name in 1966 they recruited drummer Theo Klouwer (30 June 1947 – 8 February 2001).