[net.physics] physics of harmony

mem@sii.UUCP (Mark Mallett) (08/25/83)

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Can anybody tell me, or point me to literature describing, why certain
combinations of tones are pleasing and some aren't?  That is, I'd like
to know some of the physics of harmony.  For instance, why are
major thirds, fourths, fifths & major triads pleasant?  I can
tell the ratio of the frequencies of all the notes involved, and that
the base-10 logarithms of those ratios are rather interesting.  Any
real information would be appreciated.

Mark E. Mallett
decvax!sii!mem

DCP@MIT-MC@sri-unix.UUCP (08/27/83)

From:  David C. Plummer <DCP @ MIT-MC>

Part of it is physics, part of it is history/culture, and part of
it is psychoacoustics.

Physics: I don't know of a good literary reference.  "Horns,
Strings and Harmony" (I'd give you more info but I can't find my
copy at the moment) may help.  It has mostly to do with where the
overtones fall.  I think you can safely punt the logarithms.  For
example, take a major triad which has a Pythagorean ration of
4:5:6 and a minor triad with ratios 6:7:9 and look at the
overtones (assume C is 256 for convenience).  First note that
each of these has a major and minor interval.  One major interval
is in a ratio of 4:5 and the other is 7:9, or .8 vs. .777.  The
minor intervals are 5:6 and 6:7, or .833 and .857.  This more or
less shows that the Pythagorean system is bankrupt for practical
uses.  Anyway, you will find that in the major triad more strong
overtones of the root (say the first 10) overlap with overtones
of the other notes than in the minor triad.

History: In the Medieval days (of Western culture) they really
didn't care about major scales and minor scales; they had modes.
Very few people of recent days (probably as far back as 100
years) have used modal harmonies, unfortunately.  As I recall,
the Beatles were actually the most popular to revive some of it.
But back in the Medieval days they were highly concerned with God
and the devil.  If something didn't sound quite right, it was the
devil's doing and was to be avoided.  Tritones, minor seconds and
major sevenths immediately fell into this class.  Major seconds
and minor sevenths were't far behind.  Then minor thirs/major
sixths.  The only universally accepted intervals were the octave,
perfect fourth and perfect fifth.  Even the major third and minor
sixth were sometimes avoided; you will often find cadences that
are perfect fifths and octaves with no thirds.  As the years went
on the rules got looser but the underlying philosophical base
didn't sway quite so quickly.  Also note that India and Japan
have completely different tonal systems than the West.  We may
find their music unpleasant or uninteresting because we do not
understand it.  This has been true throughout history (read up on
Beethoven or Stravinsky, for example).

Psychoacoustics: You say that major triads/intervals are
pleasant, implying minor triads/intervals are not.  Why?  Why do
people generally consider minor triads "sad"?  (It is often the
case, but not always; perhaps because of the composer's will, not
the listener's.)  Why is the key of E major "brighter" than
E-flat major?  Why is C major the most "crystaline" major key?
How many people believe in the Nyquist theory when applied to
music?  Example: is 44.1 Ksamples per second really sufficient
for digital audio disks?  (I say no.  This gives a Nyquist
frequency of 22K and with filters the upper range is diminished
to around 20K.  People will say that you can't hear above 20K
anyway.  So what?  You can't hear below 16Hz either.  You can
FEEL below 16Hz, so there is no reason there are not some subtle
interactions above 20K.)

There is only so much physics and music theory you can put into
practice before the subjective aspects show their heads, for
better of for worse.

steve@brl-bmd@sri-unix.UUCP (09/02/83)

From:      Stephen Wolff <steve@brl-bmd>


As DCP has pointed out, you've mixed physics and psychoacoustics.  There are
some of us, for example, who assert the major triad is not pleasant but
merely trite, and that one of the most interesting chords is the fundamental-
fifth-octave because of the ambiguity and mystery of the "missing" major/minor
third.

Your discussion of logarithms implies you're thinking of "equal temperament"
which did not enter widespread use until the 19th century.  For a concise
discussion of other tunings (`Pythagorean', `just', `mean-tone') look up those
terms and also `Intervals, calculation of' in the Harvard Concise Dictionary of
Music (Belknap/HUP,1978).

And there are some early music buffs who claim that 16th century string and
keyboard music (that of John Dowland, for example) doesn't sound `right'
unless the instruments are tuned in one of the mean-tone temperaments that
were in common use at that time.  But frankly my ears aren't that well-trained!