How did Moslem artists decorate the interiors of buildings ?

probably with s.u.ic.ide bombers

Explanation:

The themes used were vegetal bands for vertical or horizontal elements, marble imitations for the lower parts of long walls, chevrons or other types of borders on floors and domes, and even whole trees on the spandrels or soffits (undersides) of arches as in the Umayyad Mosque of Damascus or the Dome of the Rock;

including the octave, the answer would 8 notes in a major scale with one note being played twice. ex) c major scale includes: c, d, e, f, g, a, b, c

notice that c is played twice

however, if you were to ask me how many different notes are in a major scale- the answer would be 7.  

12-bar blues chorus = a a b