Math, Music and Mind. Musictheory.net.
Dave Conservatoire - Learn about music for free! Circle of 4ths and 5ths - Part 2: How To Memorize It. Pebberbrown. Foundations of music theory - Musical Notes. The Musical Notes are 12, 7 being natural and the other 5 are altered. The natural notes, sorted out by their pitch, from the lowest to the highest, are: C, D, E, F, G, A and B. These 7 notes form the so called C Major Scale and correspond to the “white keys” in the piano.
After the B comes another C and so on. Nevertheless, the first and second C are not identical, as the latter is higher than the former. The thing is that, from the point of view of Physics, the “vibration frequency” of the second C is exactly double that of the first C, which makes those notes very “affine” when hearing them, to the extent of assigning them the same name. The distance between two consecutive natural notes are not always the same, for in some cases the distance is one Whole step (W) and in others it is one Half step (H). Figure 1. In order to name the altered notes, the accidentals are introduced, which are the sharp ( ) and the flat ( ).
Or D . And F natural, or B natural and C ) and the double flat (