Octave species various available intervals could be combined in any order, even restricting species to just the diatonic genus would result in twelve ways of dividing the octave (and his 17th-century editor, Marcus Meibom, pointed out that the actual number is 21), but "only seven species or forms are melodic and symphonic" . Those octave species that cannot be mapped onto the system are therefore rejected . In chant theory beginning in the 9th century, the "New Exposition" of the composite treatise called "Alia musica" developed an eightfold modal system from the seven diatonic octave species of ancient Greek theory, transmitted to
Octave glissando upward with the right hand. The "Alborada del gracioso" from Maurice Ravel's "Miroirs" contains glissandi in thirds and fourths in one hand. Octave glissando An octave glissando is a glissando played on the piano by maintaining a constant distance of an octave between the thumb and finger used to execute it, and shifting the whole hand in the direction of the glissando. Due to the positions of the thumbs on the player's hands, octave glissandos are almost always executed upwards with the left hand and downwards with the right. However, exceptions include Balakirev's "Islamey", where players are instructed to execute