The keys that have two sharps (D major and B minor) have F sharp and C sharp, so C sharp is always the second sharp in a key signature, and so on. For example, if a key (G major or E minor) has only one sharp, it will be F sharp, so F sharp is always the first sharp listed in a sharp key signature. This is the same order in which they are added as keys get sharper or flatter. The sharps or flats always appear in the same order in all key signatures. This key signature has a flat on the “B” line, so all of these B’s are flat. When a sharp (or flat) appears on a line or space in the key signature, all the notes on that line or space are sharp (or flat), and all other notes with the same letter names in other octaves are also sharp (or flat). The key signature is a list of all the sharps and flats in the key that the music is in. The clef tells you the letter name of the note (A, B, C, etc.), and the key tells you whether the note is sharp, flat or natural. They appear so often because they are such important symbols they tell you what note is on each line and space of the staff. In common notation, clef and key signature are the only symbols that must appear on every staff. If there are no flats or sharps listed after the clef symbol, then the key signature is “all notes are natural”. It may have either some sharp symbols on particular lines or spaces, or some flat symbols, again on particular lines or spaces. The key signature comes right after the clef symbol on the staff.

Key signatures are generally written immediately after the clef at the beginning of a line of musical notation, although they can appear in other parts of a score, notably after a double bar.

In musical notation, a key signature is a series of sharp symbols or flat symbols placed on the staff, designating notes that are to be consistently played one semitone higher or lower than the equivalent natural notes (for example, the white notes on a piano keyboard) unless otherwise altered with an accidental.

Symbol for a flat note