Re: Music knowledge representation

[D'Arcy J.M. Cain]

On Mon, 29 Sep 2008 20:29:44 +0200
"Mr.SpOOn" <mr.spoon21@gma il.comwrote:

Couldn't the note class simply have a list of all the notes and have a
simple method calculate the actual pitch?

>
That's not really how it works. There exists just 12 octave
independent pitch classes. This means that there is a pitch class C
with all possible Cs. There ambiguities with accidentals, because
different named notes fall in the same pitch class. The difference is
important for the musical theory, because C# and Db belongs to the
same pitch class (actually they are the same note, they sounds
completely identical -- because on the piano you play them pressing
the same key), but in a scale they have a very different role.

Sure, they are enharmonically identical but in our tempered scale.
That's why my example showed it as (note, octave, accidental) rather
than a specific note. It would differentiate between these.

For example, the interval C F# is an "augmented fourth", because what
really matters are the natural note (C and F), and their distance if
4. Then it is augmented due to the #-
>
But the interval C Gb (Gb is the same as F#) is a "diminished fifth".

This is true. My simple example would not have dealt with this. The
arguments would have to be the full tuple rather than the actual pitch.

So I can't list all pitches.

You can but you can't store them as raw pitches.

def interval(self, lower, higher)
if lower higher:
# uncomment one of the two following lines depending
# on the behaviour you want
#lower,higher = higher,lower
#higher += 12

# could use some error trapping
return self.interval_n ame[higher - lower]

Note that lower and higher could be a note object that you have to
convert to integers first.

>
I can't estabilish which note is higher, because all the analysis part
is octave independent. Anyway thanks for the ideas.

I'm not sure I understand this. You either have to assume that the
first note is the root or the lower one is. What other options are
there? It sounds like your requirement is "higher += 12" or some
variant. It also depends on whether you need to deal with things like
ninths and thirteenths.

Anyway, I was just tossing out ideas. You know what your requirements
are better than I.

--
D'Arcy J.M. Cain <darcy@druid.ne t | Democracy is three wolves
http://www.druid.net/darcy/ | and a sheep voting on
+1 416 425 1212 (DoD#0082) (eNTP) | what's for dinner.

[Aaron \Castironpi\ Brady]

Re: Music knowledge representation

On Sep 29, 3:56 pm, "D'Arcy J.M. Cain" <da...@druid.ne twrote:

On Mon, 29 Sep 2008 20:29:44 +0200
>
"Mr.SpOOn" <mr.spoo...@gma il.comwrote:

Couldn't the note class simply have a list of all the notes and have a
simple method calculate the actual pitch?

>

That's not really how it works. There exists just 12 octave
independent pitch classes. This means that there is a pitch class C
with all possible Cs. There ambiguities with accidentals, because
different named notes fall in the same pitch class. The difference is
important for the musical theory, because C# and Db belongs to the
same pitch class (actually they are the same note, they sounds
completely identical -- because on the piano you play them pressing
the same key), but in a scale they have a very different role.

>
Sure, they are enharmonically identical but in our tempered scale.
That's why my example showed it as (note, octave, accidental) rather
than a specific note.  It would differentiate between these.
>

For example, the interval C F# is an "augmented fourth", because what
really matters are the natural note (C and F), and their distance if
4. Then it is augmented due to the #-

>

But the interval C Gb (Gb is the same as F#) is a "diminished fifth".

>
This is true.  My simple example would not have dealt with this.  The
arguments would have to be the full tuple rather than the actual pitch.
>

So I can't list all pitches.

>
You can but you can't store them as raw pitches.
>

   def interval(self, lower, higher)
       if lower higher:
           # uncomment one of the two following lines depending
           # on the behaviour you want
           #lower,higher = higher,lower
           #higher += 12

>

       # could use some error trapping
       return self.interval_n ame[higher - lower]

>

Note that lower and higher could be a note object that you have to
convert to integers first.

>

I can't estabilish which note is higher, because all the analysis part
is octave independent. Anyway thanks for the ideas.

>
I'm not sure I understand this.  You either have to assume that the
first note is the root or the lower one is.  What other options are
there?  It sounds like your requirement is "higher += 12" or some
variant.  It also depends on whether you need to deal with things like
ninths and thirteenths.
>
Anyway, I was just tossing out ideas.  You know what your requirements
are better than I.
>
--
D'Arcy J.M. Cain <da...@druid.ne t        |  Democracy is three wolveshttp://www.druid.net/darcy/               |  and a sheep voting on
+1 416 425 1212     (DoD#0082)    (eNTP)   |  what's for dinner.

I like D'Arcy's tuples so far. You could have a 4th element that
contains adjustment for temper. Octave could be None.

You want ( 4, None, 1 ) "sharp 4th" == ( 5, None, -1 ) "flat 5th", but
you can't have it. The closest ones are Note( 4, None, 1 )== Note( 5,
None, -1 ) or Note(4, None, 1 ).enh_cmp( Note( 5, None, -1 ) ). More
elaborate code means more options for calling, though: Note(4, None,
1 ).cmp_enh( 5, None, -1 ), and just call the constructor on the 3
arguments. You also want Note( 9, None, 0 ).cmp_octave( 2, Rel+ 1,
0 ), 9th== 2nd + 1 octave, and Note( 9, None, 0 ).cmp_nooctave( 2,
None, 0 ), where cmp_... functions return in ( -1, 0, 1 ), and the
middle term can be a class Relative instance, which indicates a
relative octave instead of absolute... or just start at 4.