# compress the orchestra

Started by October 14, 2019
```Occasionally I attend recitals, where the student
performs a concerto.  It's a bit of a financial
stretch for the music department to hire an orchestra,
so a second pianist accompanies, acting as the orchestra.

Thus someone has to condense the entire orchestral section
down to a single instrument!  A mighty job of compression
indeed.  How do they do that?  The conductor isn't a
mathematician, yet manages a feat beyond anything you'd
find in a text.

How would you tackle this one?

--
Rich

```
```On Tuesday, October 15, 2019 at 11:11:44 AM UTC+13, RichD wrote:
> Occasionally I attend recitals, where the student
> performs a concerto.  It's a bit of a financial
> stretch for the music department to hire an orchestra,
> so a second pianist accompanies, acting as the orchestra.
>
> Thus someone has to condense the entire orchestral section
> down to a single instrument!  A mighty job of compression
> indeed.  How do they do that?  The conductor isn't a
> mathematician, yet manages a feat beyond anything you'd
> find in a text.
>
> How would you tackle this one?
>
> --
> Rich

Well you cannot. You just do the main themes.
```
```<gyansorova@gmail.com> wrote:

>On Tuesday, October 15, 2019 at 11:11:44 AM UTC+13, RichD wrote:

>> Occasionally I attend recitals, where the student
>> performs a concerto.  It's a bit of a financial
>> stretch for the music department to hire an orchestra,
>> so a second pianist accompanies, acting as the orchestra.
>>
>> Thus someone has to condense the entire orchestral section
>> down to a single instrument!  A mighty job of compression
>> indeed.  How do they do that?  The conductor isn't a
>> mathematician, yet manages a feat beyond anything you'd
>> find in a text.
>>
>> How would you tackle this one?

A suitably-talented musician arranges the orchestral piece into a piano
arrangement.

(This has little to do with the conductor.)

I would believe for major orchestral pieces, such arrangements already
exist and can be purchased.  The pianist of course needs to sight-read
the piece, but that part is routine.

>Well you cannot. You just do the main themes.

I imagine that is the basis of it.

Steve
```
```On October 14, Steve Pope wrote:
>>> Occasionally I attend recitals, where the student
>>> performs a concerto...
>>> so a second pianist accompanies, acting as the orchestra.
>>> Thus someone has to condense the entire orchestral section
>>> down to a single instrument!  A mighty job of compression
>>> indeed.  How do they do that?  The conductor isn't a
>>> mathematician, yet manages a feat beyond anything you'd
>>> find in a text.
>>> How would you tackle this one?
>
> A suitably-talented musician arranges the orchestral piece into a piano
> arrangement.

um, yeah
How does he do that?

> I would believe for major orchestral pieces, such arrangements already
> exist and can be purchased.

um, yeah
How were they created?

>> Well you cannot. You just do the main themes.

um, yeah

This is a DSP group, information theory and all that.
The source compression bit splits into a lossless part,
and the more practical, difficult lossy part.

Obviously, condensing an orchestra down to a single
instrument (the piano or violin soloist is fixed) is lossy.
How does one identify the main themes, algorithmically?

> I imagine that is the basis of it.

OK, let's go with that - what set of basis functions are

With Fourier spectral analysis, one simply picks the
largest magnitude components.   That's a doubtful method, here.

You're given this task as a paid project.  You have to
deliver a source compression program...

The point is, music theorists can do this, have done it.
What's their secret sauce?

--
Rich
```
```RichD  <r_delaney2001@yahoo.com> wrote:

>On October 14, Steve Pope wrote:

>> A suitably-talented musician arranges the orchestral piece into a piano
>> arrangement.

>um, yeah
>How does he do that?

Study piano from age 6, music theory from age 12, go to a conservatory
and make the grade and they can do that.

Just like musicians would say to us engineers, "how do you do that?"

>> I would believe for major orchestral pieces, such arrangements already
>> exist and can be purchased.

>um, yeah
>How were they created?

See above ... by suitably trained musicians.

>This is a DSP group, information theory and all that.

(La-dee-fucking-da)

>The source compression bit splits into a lossless part,
>and the more practical, difficult lossy part.

>Obviously, condensing an orchestra down to a single
>instrument (the piano or violin soloist is fixed) is lossy.
>How does one identify the main themes, algorithmically?

>OK, let's go with that - what set of basis functions are

>With Fourier spectral analysis, one simply picks the
>largest magnitude components.   That's a doubtful method, here.

>You're given this task as a paid project.  You have to
>deliver a source compression program...

I would hire a professional musician, rather than believing that
DSP is some sort of holy grail for all tasks in the world.

Hint: many in the real world are just not down with engineers
believing they can replace musicians.   It's bad form at minimum...
some would call us scabs.  Musicians who can do this are paid
union scale.

Steve
```
```RichD  <r_delaney2001@yahoo.com> wrote:

>Obviously, condensing an orchestra down to a single
>instrument (the piano or violin soloist is fixed) is lossy.
>How does one identify the main themes, algorithmically?

>OK, let's go with that - what set of basis functions are

>With Fourier spectral analysis, one simply picks the
>largest magnitude components.   That's a doubtful method, here.

>You're given this task as a paid project.  You have to
>deliver a source compression program...

One other observation:

For this arranging task, one is not working with the time domain
(audio) signals.  One is working in the frequency domain, because musical
scores are already "transformed" into the frequency domain,
because they define the amplitude of musical notes.  Nor is arranging
a real-time action.

For arranging, the task is score (frequency domain) in, score (frequency
domain) out.  There is no time-domain signal in the chain.

For performing on an instrument from a score, the task is score
(frequency domain) in, audio (time domain) out.

For scoring/notating, or (most?) compostion, the task is audio
(time domain) in, score (frequency domain) out.

There's a fourth possibility -- time domain in, time domain out.
I will say that corresponds to improvisation, singing in harmony,
and various other things that musicians know how to do.

Steve
```
```On Mon, 14 Oct 2019 15:11:40 -0700 (PDT), RichD
<r_delaney2001@yahoo.com> wrote:

>Occasionally I attend recitals, where the student
>performs a concerto.  It's a bit of a financial
>stretch for the music department to hire an orchestra,
>so a second pianist accompanies, acting as the orchestra.
>
>Thus someone has to condense the entire orchestral section
>down to a single instrument!  A mighty job of compression
>indeed.  How do they do that?  The conductor isn't a
>mathematician, yet manages a feat beyond anything you'd
>find in a text.
>
>How would you tackle this one?
>
>--
>Rich
>

Have you ever read a synopsis for a movie?    Tell the whole story and
all the imagery in a few paragraphs!   How do they do that!   That's
an extremely high compression rate.

```
```RichD wrote:
> Occasionally I attend recitals, where the student
> performs a concerto.  It's a bit of a financial
> stretch for the music department to hire an orchestra,
> so a second pianist accompanies, acting as the orchestra.
>
> Thus someone has to condense the entire orchestral section
> down to a single instrument!  A mighty job of compression
> indeed.  How do they do that?  The conductor isn't a
> mathematician, yet manages a feat beyond anything you'd
> find in a text.
>
> How would you tackle this one?
>
> --
> Rich
>

The job is called "arranging". It's  "grey art" - a bit art,
a bit science.

You'd be amazed how much you can remove from an arrangement and still
have the piece be recognizable.

--
Les Cargill
```
```Am 16.10.19 um 02:38 schrieb RichD:
> On October 14, Steve Pope wrote:
>>>> Occasionally I attend recitals, where the student
>>>> performs a concerto...
>>>> so a second pianist accompanies, acting as the orchestra.
>>>> Thus someone has to condense the entire orchestral section
>>>> down to a single instrument!  A mighty job of compression
>>>> indeed.  How do they do that?  The conductor isn't a
>>>> mathematician, yet manages a feat beyond anything you'd
>>>> find in a text.
>>>> How would you tackle this one?
>>
>> A suitably-talented musician arranges the orchestral piece into a piano
>> arrangement.
>
> um, yeah
> How does he do that?
>

For most parts this is actually quite simple. Your question is posed in
a way as if it were necessary for a symphonic orchestra with, say, 60
musicians, that everyone is always there and plays a different part than
their neighbours. This is not true. You typically have, e.g. 4 second
violins all playing nearly the same thing. When you take this redundancy
out, you'll end up with maybe 8 voices.

And then, still these are not playing in a chaotic way, but European
music has a structure of melody + accompaniment, where the melody can be
a single voice and the accopmaniment plays chords (C major, a minor,
....). For most of the parts in a piece, therefore you could sing the
melody and play the chords on a guitar, to render the piece in a
recognisable way.

On a piano, you can play a few simultaneous voices on one hand and the
chords on the other hand, that's what they do. So you would read the
score, decide which is the dominant melody - often played by the solo
musicians and marked up, or played by many in parallel -, extract the
chord from the other notes and replace these second voices by the chord,
which is played in the correct rhythm. With some training it is possible
to do that in "real time", i.e. you know the piece well enough, then you
can play this in a recognisable fashion.

Typically there are a few bars in the piece where this goes wrong, and
one has to think more, but for the majority of the bars you can do that
"by ear".

Christian
```
```On 10/17/2019 18:20, Steve Pope wrote:
> RichD  <r_delaney2001@yahoo.com> wrote:
>
>> Obviously, condensing an orchestra down to a single
>> instrument (the piano or violin soloist is fixed) is lossy.
>> How does one identify the main themes, algorithmically?
>
>> OK, let's go with that - what set of basis functions are
>
>> With Fourier spectral analysis, one simply picks the
>> largest magnitude components.   That's a doubtful method, here.
>
>> You're given this task as a paid project.  You have to
>> deliver a source compression program...
>
> One other observation:
>
> For this arranging task, one is not working with the time domain
> (audio) signals.  One is working in the frequency domain, because musical
> scores are already "transformed" into the frequency domain,
> because they define the amplitude of musical notes.  Nor is arranging
> a real-time action. >
> For arranging, the task is score (frequency domain) in, score (frequency
> domain) out.  There is no time-domain signal in the chain.
It's clearly not that simple.  The score is not pure frequency domain is
a time-sequence of notes.
>
> For performing on an instrument from a score, the task is score
> (frequency domain) in, audio (time domain) out.
>
> For scoring/notating, or (most?) compostion, the task is audio
> (time domain) in, score (frequency domain) out.
>
> There's a fourth possibility -- time domain in, time domain out.
> I will say that corresponds to improvisation, singing in harmony,
> and various other things that musicians know how to do.
>
> Steve
>

--
Best wishes,
--Phil
pomartel At Comcast(ignore_this) dot net
```