Hexachord

A hexachord (Greek hexa " six " CHORD " string " ) in music theory, a series of six consecutive tones or pitch classes.

Hexachords in the Middle Ages

In the medieval music theory hexachords formed (presumably derived from the sounds of the six-string lyre ) the basis for learning Gregorian chant. Various hexachords are thinking as overlapping excerpts from throughout the former Tonvorrat from G to e ".

The hexachord is an extension of the Greek tetrachord ( efga ), which was in the 9th century a tone shifted downward ( at about Hucbald ) on the fundamentals of the four church modes (d, e, f and g). Above and below each a whole step was to these four tones added ( c and a ). In any Hexachord the two middle notes are a half step, whole step every other one apart.

The hexachords were built on C, G or F, accordingly, there were three types of Hexachorden: the Hexachordum naturale (natural hexachord ) CDEFGA, the Hexachordum durum (hard hexachord ) GAHCDE and Hexachordum molle ( soft hexachord ) FGABCD. Through seven hexachords (on G, c, f, g, c ', f ' and g ') of the gamut of medieval music of almost three octaves (G -e " ) was covered and divided.

Guido of Arezzo highlighted the tones of the hexachord with the solfeggio and differ depending ut, re, mi, fa, sol, la, which are the John hymn Ut queant laxis removed. As an aid might have served him, but certainly later masters of the Middle Ages, the so-called guido African hand.

B durum and b molle

Originally there had been only the B level between the pitches A and C. The system of hexachords meant that there were two varieties of the B: b durum ( "hard B"; corresponds to the current H) and b molle ( " soft B"; corresponds to the current B). On these terms, ultimately, the designation of major, minor, goes back. The major third of the major triad on G ( GHD ) is formed with a b durum (H). The minor third of the minor triad on G ( GBD) is formed with a b molle (B).

In the written fixation of the tone name is used to distinguish the b durum ab quadratum ( " Square B" ) and for the b molle a b rotundum ( "round B"). Depending on requirements, the ( lowercase ) B was drawn differently: It was edged shaped ( b quadratum ) when forming the semitone interval with the C, so it should be higher. It has a rounded shape ( b rotundum ) when forming the half-tone to the interval A, therefore should be lower.

After numerous variations on this calligraphy eventually evolved from the b quadratum and b rotundum today accidentals and sign.