What do you mean by four beats per bar and one beat per quarter note?

Take quarter notes as a beat, and four beats per bar are 4/4 beats. Four beats in a bar, that is, there is no horizontal line below the note, and there is no dot and horizontal line behind it. Together, these four notes are called whole notes, so each note is a quarter of the whole note and is called a quarter note. There are several beats in a bar, that is to say, how many beats repeat a rhythm cycle; Now let's take a quarter note as a beat, four beats per bar.

Taking a quarter note as a beat is to specify the speed of a piece of music conveniently. It is usually stipulated how many beats a piece of music has per minute, that is, how many quarter notes there are per minute. If an eighth note is specified as a beat, how many beats per minute, that is, how many eighth notes are there per minute.

Extended data

Each beat has its own rhythm strength law, which can only be felt if it appears repeatedly. 4/4 beat strong, weak, strong, weak. The symbol of 4/4 beat is located at the beginning of the staff, and its size occupies five elements.

In addition to 4/4 beats, there are 3/4 beats and 2/4 beats; And if we take the eighth note as a beat, 6 beats per bar is what we see as 6/8 beats; Each beat has its own rhythm law. Only by appearing repeatedly can we feel the existence of rhythm. Four-quarters of the beat is strong, weak, sub-strong and weak, three-quarters are strong, weak and weak, two-quarters are strong and weak, and six-eighths are strong, weak and sub-strong and weak.

References:

Baidu encyclopedia-four or four beats