Re: [Rosegarden-devel] Transposition strategies

[Heikki J. J. <hj...@gm...>]

2007/6/14, Nick Bailey <n.j...@el...>:
>
> On Sunday 10 June 2007 15:55:45 D. Michael McIntyre wrote:
> > On Saturday 09 June 2007, you wrote:
> > > So the piece should sound the same, simply look different?
> >
> > Right.  More broadly, we really need an easy way to flip around between
> > written transpositions....
> > That looks like just the sort of "you break it, you bought it" thing I
> was
> > talking about.  :)  This stuff is really tricky to get right.  It seems
> so
> > simple on the surface, but it's so easy to miss the edge cases, and so
> hard
> > to get them working without breaking something in the middle.
>
>
> Hear, hear!
>
> And the reason it's hard to get right is also wrapped up in the coding
> ideal
> of Rosegarden: that it shouldn't get in the way of doing MIDI I/O easily.
> We
> were (I hope) very careful to follow this lead, which is a good one, with
> our
> microtonal and pitch-tracker patches. But when it comes down to it, MIDI
> is a
> highly inadequate representation of musical information (as already noted,
> it
> can't even distinguish enharmonic equivalents, for example!)


MIDI should be an approximation of the notation. (notation->midi) If changes
are done in
notation side, the effects are predictable. (midi->notation?) But if changes
are made in MIDI
side, the changes in notation side may depend from case to an another,
because information is lost in the approximation.

There are several other way of storing pitch, such as Base-40 or Binomial
> representations (pitch class/spelling), but we think the only real way to
> do
> it is to use a circle-of-fifths representation. We're working on one which
> should handle almost everything including 19-ET etc microtonality. It's
> only
> assumption is that all music is diatonic. And it makes transposition
> really
> easy.


Also, it is only assumption that music fits to any quantization of pitches.
Think of
a glissando which is played with violin or trombone.

But then you'd have to be explicit about how you get from the note's pitch
> to
> its frequency. MIDI completely ignores this step. Musicians call
> it "temperament", and the results of just shoe-horn-ing everything into
> 12-ET
> are shocking (there's a good little applet to show you just how out of
> tune
> we all are here:
>
>         http://www.j2b.co.uk/tuning
>
> :) ) Only keyboard players use anything like ET. Everyone else bends
> everything. There's the MIDI tuning standard, but not very many
> applications
> support that.


Even pianos are often not exactly tuned into equal temperement (ET), but the
higher notes may be tuned sligtly over. The reason may lie in physics: When
you hit a note which is very low, the string in piano becomes longer and
more stressed, which increases its tuning. After few vibrations, the tuning
of the string in piano becomes lower as the amplitude of oscillation
decreases.

Of course, these effect should not appear in notation.

But do you want all this stuff in a sequencer? I doubt it, at least not as a
> high priority. The pitchtracker supports temperament through the use of
> tuning files. It depends where you chose to draw the line, I guess.
>
> Nick/.
>
> http://www.n-ism.org


IMHO, handling microtonalism is a difficult problem, especially, if you
think that a single tone
consist of the base tone and its second, third, etc. harmonics. Does some
other base approximate more efficiently the 2nd, 3rd, 4th, and 5th harmonic
tones of a base tone, than 12-ET does?

It is easier to consider only the base tone, to fix notes into 12-ET and to
give each note an adjustment in tuning, if it deviates from 12-ET.

Of course, the music notation commonly used is just 12-ET approximation of
the performed music. What you hear in a music performance depends on very
many things, like the instrument, players mood, acoustics,  hearers personal
ear,  humidity, background sounds, resonances to the environment, etc. What
is interesting that the 12-ET system works so well.

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-- 

Heikki