If an eighth note is half the duration of a quarter note, would the duration of an eighth note played at 60bpm be equal to the duration of a quarter note at 120bpm? If yes, why was the concept of different notes, like half, quarter, eighth, formed?
Wouldn't it be easier to have just one base/reference note and vary the tempo of the song whenever necessary?
Because if the first para is true, then having an 8th/16th note would be the same as changing the tempo of a quarter note to make it twice or 4 times as fast