I would like to say first that I am no expert in this field.  However,
there certainly are a number of obstacles that need to be overcome for
this sort of program to be developed.  As mentioned before, the biggest
problem is that when a piano, or nearly any musical instrument plays,
"one note" is not really "one note" -- there are always many overtones
in a given note, and this becomes confusing to machines as we know them
today.

In my business (repair of woodwind/brass instruments) we quite often
are asked to check the intonation of an instrument.  Even a new model
"high-end" electronic tuner can get confused.  For instance, you might
play a C on an oboe, but the tuner claims you are playing a G.  This is
because the first G overtone is so strong that it 'hears' that more
than the fundamental.

Now, it seems that if you had an instrument that only played very pure
tones, it would be much easier to write a program that would be able to
decipher the notes correctly.  Unfortunately, this is not the real
world of musical instruments.  I doubt anyone would even want to listen
to music performed with pure tones for very long -- it would be an
assault on the ears!

Then we have the ethical questions involved in the use of such a
program.  Many might consider it a great boon to people and musicians,
others would take the opposite view.  Writers of music make money from
the sale of their music, be it in recorded format or printed format.
If a program existed that would allow anyone to take any recording and
put it through the program and have a printable/editable copy of the
music, one is certainly then taking away from the livelihood of the
composer.  If you want a copy of the music, buy it.

Unfortunately, for much of history, people have been looking for ways
to make and have music without having to pay for it.  Buy a recording
of an orchestra and you can listen to it as many times as you want for
one fee; go to a concert and you only hear it once (for probably a
much higher fee).  Instead of going to hear a live piano performance,
hey, buy a piano roll and you can hear it as often as you want.  The
bar doesn't want to hire a band?  Put in a jukebox.  Music used to be
much more of a participatory thing, now it's a passive thing.  (But,
I digress....)

Would using such a program not be akin to reverse-engineering?  Is it
right to do this to someone else's work?  Do we really want the day to
come when there is no new music being written since there is no
financial incentive to do so?

Regards,
John W Miller
http://www.PianoRollStuff.com/

 [ None-for-note manuscripts of a piano performance are rarely
 [ published, so it's not likely a publisher will be offended.
 [ Certainly the composer and artist are due their royalties if the
 [ new setting (a MIDI file or a piano roll) is sold or performed
 [ in public.  It's more than ethics, it's the law.  -- Robbie