Minor scale based on the accidentals of the "natural" minor scale, not on those of the harmonic or melodic minor scales. For example, a piece in E minor will have one sharp in its key signature because the E natural minor scale has one sharp (F). Major and minor keys that share the same key signature are "relative" to each other. For instance, F major is the relative major of D minor since both have key signatures with one flat. Since the natural minor scale is built on the 6th degree of the major scale, the tonic of the relative minor is
C-flat major and is now playing in B major, marked with the necessary sharps and naturals as accidentals. This use of C major in harp parts when the rest of the orchestra is playing in B major is not exceptional: it is standard practice in orchestral music written in B major for harp parts to be notated in C major. In Arnold Bax's symphonic poem "Tintagel", the key is B major and again the harp part is always notated in C major; but in this case the harp's key signature contains only 6 flats, and the necessary Fs are notated with accidentals.