In music, pitches are denoted by letters ranging from A to G, where A is the lowest pitch and G is the highest pitch. These letters are the note names. Western musicians in the European tradition created standards for defining pitches by assigning a standard pitch reference -- a specific frequency -- to A and defining the distances between pitches in steps. The pitch A that is above middle C is defined as having a frequency of 440 Hertz. Hertz is a measure of vibrations per second. B is one step up in pitch from A.
Notes may be followed by a symbol indicating whether the note is sharp or flat. Sharp and flat notes lie between whole notes, such as A-sharp, which is a half-step up from A and a half-step down from B. In musical notation, a sharp note occurs when a note is higher in pitch than the note that precedes it. For example, A-sharp is above A in pitch. If the note is lower than the note that precedes, it is flat. For example, A-flat is below B in pitch.
The symbols on the musical staff are called notes. Notes are organized according to their pitches. Notes with lower pitches are drawn on the bottom of the staff, while notes with higher pitches are drawn on the top of the staff. A symbol denotes whether the note is sharp or flat.
An octave is divided into 12 notes, ranging from A to G-sharp. Instruments, such as guitars and pianos, allow musicians to play notes that cover more than one octave. A full-size piano has seven octaves, 88 keys and 12 keys per octave. When one octave ends and another begins, you cycle through the notes again, starting with note A. The lowest note on a full-size piano using standard tuning is called A0. The "0" denotes the octave. A1 is a whole octave above A0 and it has a higher pitch than A0.