Musical note commonly), a double sharp sign on a key signature with a single sharp indicates only a double sharp, not a triple sharp. Assuming enharmonicity, many accidentals will create equivalences between pitches that are written differently. For instance, raising the note B to B is equal to the note C. Assuming all such equivalences, the complete chromatic scale adds five additional pitch classes to the original seven lettered notes for a total of 12 (the 13th note completing the octave), each separated by a half-step. Notes that belong to the diatonic scale relevant in the context are sometimes called "diatonic notes";
Diatonic scale Pythagorean tuning: Six of the "fifth" intervals (C–G, D–A, E–B, F–C', G–D', A–E') are all = 1.5, but B–F' is the discordant tritone, here ≈ 1.423828125. Extending the series of fifths to eleven fifths would result into the Pythagorean Chromatic scale. It would add pitches for the five "piano black key" notes, for instance A–E–B–F–C–G–D–A–E–B–F–C–G. A and G are commonly thought of as being the same note, but as worked out in this way, G is higher pitch than A by about 1.01364 (, the Pythagorean comma, about 24% of a semitone, = ). Depending on whether one chooses A