1=bA This is the "key signature" mark in the notation, which means that the tonality of this piece of music is a flat major. It is to use the sound of A flat as the tonic (do) of the scale.

key is the fixed height of music, and key signature is the symbol of key. In the notation, key signature is written in the upper left of the beginning of the music, and in the staff, the tick mark is written behind the clef at the beginning of each staff, and the rising and falling marks behind the clef are key signature.

Extended information

Brief introduction of key signature: The tone change sign written after the clef in the staff is called key signature. In modern European music theory, the reason why the tonality is expressed by key signature is because the concept of tonality in Europe is often grasped by its expression on keyboard and staff.

The same natural heptatonic scale, when the player chooses different laws from the twelve laws to form different key ranges, it shows different key selection methods on the keyboard.

because black keys's notation on the staff is represented by adding # or b in front of the notes of the white key phoneme, a number of black keys included in the key range is also represented by a number of # or b on the staff, and these ascending and descending marks are written on the left side of each line of the staff table and the right side of the clef, which becomes the symbol of the key range used by the music.

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