Utrolige påstander her, omkring matematikkens fravær i musikk. Sykliske og dihedrale kanoniske grupper, slik Bach utviklet dem, er grunnlag for gruppeteori i matematikk, for eksempel. Bach var en mestermatematiker, men han skrev med noter fremfor tall.
La oss kikke litt på Bach - hva med hans "puzzle canons"? Hvordan skulle man løst gåtene uten matematikk? Kanon-teknikken fungerer ellers overhodet ikke uten en ekstremt presis bruk av tid (som Snickers henviser til), og er fullkomne matematiske konstruksjoner.
The Musical Offering (which was dedicated to King Frederick
the Great, and based on a theme composed by him) contains two
fugues, ten canons and a trio sonata all incorporating the royal
theme in some form. The canons in particular are intriguing:
Bach wrote them out as puzzle canons, with only the first part
explicitly present and cryptic instructions to complete them
with the second part.
Eller hva med hans bruk av Pytagoras pentatoniske skala, og hans utfordring av den pure versjonen av samme gjennom Det veltempererte klavér? Bach kan vi nok trygt gå ut fra hadde perfekt gehør, og følgelig må det ha vært en lidelse å oppleve de små unøyaktighetene som datidens stemme-modul skapte etterhvert som man beveget seg opp oktavene. Følgelig kjempet han for innføring av en annen "temperering" av instrumentet, der man bevisst og matematisk fordreide tonene slik at man ikke trengte mer enn tolv i skalaen - beskrevet slik:
This situation is often expressed by saying that the circle of
fifths does not close . By this is meant the fact that if one follows
the procedure of raising a note by a fifth repeatedly, lowering it
an octave when necessary to keep within the initial octave, one
never recovers the original note. However, after twelve steps one
does recover what is extremely close to the original note. More
precisely,
(3/2)12 = 129.74 ... 27 = 128
so raising a note twelve fifths and lowering it seven octaves
brings it to 1.013 ... times its original value. It would be nice if it
were exactly the original value but that is a mathematical
impossibility.
The suggestion that arose in the seventeenth century was to
slightly flatten the fifth, to close the circle of fifths. In other
words, define the C-G interval to be 27/12 ~ 1.498, rather than 1.5
exactly, and calculate all other notes by the same technique of
moving up a fifth from the preceding note. It turns out that with
this procedure one needs only twelve notes in the scale: B# is
exactly the same as C, C# is exactly the same as Db, and so on;
the ratio of any two successive notes is precisely 21/12.
Suppose one restricts oneself to intervals less than an octave (that
is, frequency ratios between 1 and 2), and defines their combination
modulo the octave: for instance, two fifths (3/2 and 3/2)
combine to give the second (9/8), rather than 9/4. Then the set
of all possible intervals forms a group, but this group has an
infinite number of elements. The set of intervals that actually
exist on a keyboard tuned to the natural scale cannot form a
group, since most of the intervals when combined dont form
other intervals which exist on the keyboard. The equally
tempered scale, however, does form a group with only twelve
elements, 2 n/12 where n = 0, 1, 2, ... , 11.
Of course, this plays havoc with all the nice integer ratios which
we listed before: none of them survive, except the octave
indeed, they all become irrational. To suggest destroying the
purity of the fifth and the fourth requires great boldness, and
purists werent pleased. The point of the suggestion was that the
effect was actually not so bad as that of playing a scale on a piano
tuned perfectly to a very remote scale. To most ears, the difference
between these equally spaced 12 notes and the ideal ones is
hardly perceptible. And while no key will now be perfectly in
tune, no key will be more out of tune than any other. The
question was whether it was worthwhile to sacrifice a small
amount of purity of pitch in favour of vastly greater freedom in
modulation.
Bachs svar ble JA, og det kan ettertiden være glad for. Dette medførte enorme forandringer i både musikalske muligheter og i utøvelsen av musikk, og matematikere (komponister) etter Bach kastet seg over mulighetene. Beethovens lærer forlangte at Beethoven skulle lære samtlige Veltempererte matematiske utlegninger utenat, Mozart utviklet sitt kontrapunktiske arbeid fra samme.
Bach was not the originator of this idea of equal temperament,
but he was the first major composer to promote it vigorously.
Before him, composers were content to compose keyboard music
restricting themselves to keys close to C major. To emphasize the
freedom offered by the new system, Bach wrote book I of The
WellTempered Clavier : the book contained 24 preludes and 24
accompanying fugues, one in each of the major and minor keys.
(Since there are now exactly twelve notes in the octave, there are
only twelve distinct major keys and twelve minor keys: for
instance F sharp major is no longer different from G flat major).
Many years later he wrote another similar volume, which again
traversed the keys in 24 preludes and fugues. This volume was
untitled and is generally referred to as Book II of the WTC. The
Well-Tempered Claviers mission of promoting the equitempered
scale succeeded: it is the only system used to tune keyboards
today. But musically, too, the work profoundly influenced a
number of composers. Beethoven, for instance, was made by his
teacher to memorize the whole work, and for the rest of his life
kept a portrait of Bach on his desk; his late works display a
preoccupation with fugal writing. Mozart discovered Bach late
in life but the discovery sparked an interest in contrapuntal
writing evident in his later works. Chopin, in a reference to the
WTC, wrote a set of 24 preludes, with a similar tour of the keys.
He told students to always play Bach. In this century, Shostakovich
wrote a set of 24 preludes, and later another set of 24
preludes and fugues: his version of the WTC, but little-known,
and recorded for the first time only in the 1980s.
Musikk og matematikk er uadskillelige. En hvilken som helst musikalsk progresjon som lyder "rett" for et kondisjonert øre er egentlig en utledning av en matematisk progresjon man like gjerne kunne satt to streker under svaret på. Når det lyder falsk er ligningen også falsk.