The remaining five notes of the chromatic scale (the black keys on a piano keyboard) were added gradually; the first being B, since B was flattened in certain modes to avoid the dissonant tritone interval. This change was not always shown in notation, but when written, B (B-flat) was written as a Latin, round "b", and B (B-natural) a Gothic script (known as Blackletter) or "hard-edged" b. These evolved into the modern flat () and natural () symbols respectively. The sharp symbol arose from a barred b, called the "cancelled b".