The demon Murmur appears in the grimoires Book of Incantations, The Discoverie of Witchcraft, Pseudomonarchia Daemonum, and The Lesser Key of Solomon
From The Lesser Key of Solomon, Crowley/Mathers edition:
The Fifty-Fourth Spirit is called Murmur, or Murmus, or Murmux. He is a Great Duke, and an Earl; and appeareth in the Form of a Warrior riding upon a Gryphon, with a Ducal Crown upon his Head. There do go before him his Ministers with great Trumpets sounding. His Office is to teach Philosophy perfectly, and to constrain Souls of the Deceased to come before the Exorcist to answer those questions which he may wish to put to them, if desired. He was partly of the Order of Thrones, and partly of that of Angels. He now ruleth 30 Legions of Spirits. And his Seal is this, etc.
This demon was of the angelic order Throne