Major seventh the same number of staff positions, but consist of a different number of semitones (nine and twelve). The easiest way to locate and identify the major seventh is from the octave rather than the unison, and it is suggested that one sings the octave first. For example, the most commonly cited example of a melody featuring a major seventh is the tonic-octave-major seventh of the opening to "(Somewhere) Over the Rainbow". "Not many songwriters begin a melody with a major seventh interval; perhaps that's why there are few memorable examples." However, two songs provide exceptions to this generalisation: Cole Porter's
Octave illusion Lamminmaki et al. (2012) in MEG studies provide an explanation of the illusion at the neurophysiological level that is in accordance with Deutsch’s two-channel model. Octave illusion The octave illusion is an auditory illusion discovered by Diana Deutsch in 1973. It is produced when two tones that are an octave apart are repeatedly played in alternation ("high-low-high-low") through stereo headphones. The same sequence is played to both ears simultaneously; however when the right ear receives the high tone, the left ear receives the low tone, and conversely. Instead of hearing two alternating pitches, most subjects instead hear a single tone