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About MP3 to MIDI
This news about
intelliScore's polyphonic pitch recognition
published on P-ART
In the INSANE
HOLLOW-pages of my P-ART homepage I explain how Music for a ritual
dance (1984) - that's a tape composition of mine - builds the
background of my Installation
for ritual dance (1987). Since that time, I've been dreaming of a
tape-to-score converter to play my polyphonic tape compositions from
In the nineties I used the pitch-to-midi converter (Roland CP-40) in an
experimental way to convert monophonic audio performances of mine into
Further more, I used new MIDI- recording facilities to compose in realtime
as a performer. Building a MIDI-scanner under the keyboard of my grand
piano on the one hand and an intuitive music notation software on the
other, made it possible to make scores without writing out note after
note, so that I could play it as it came to me.
Actually, many computer based problems still have to be solved to convert
polyphonic music into scores. With Melodyne (http://www.celemony.com) I
can only record single melody tracks and save them as notes in
their position in time and pitch, and respecting the phrasing of the
melody line. You can even simply take a note and move it to any pitch or
time position you like. The transition between notes will always be kept
in a way that musically makes sense, and automatic formant correction
always makes the moved note sound the way you expect it to.
Polyphonic pitch recognition is really very complex. However,
advances with regard to signal separation and polyphonic harmonic tracking
which are part of the 'polyphonic pitch-to-MIDI' problem, have been made.
It might still help to understand how our auditory perception works, and
if it is only for the reason that perception is an additional (even
creative) process rather than one of pure analysis. Like the decimal
'software'system in our brain on an underlying "neuro-binary"
system, the computer is able to do decimal arithmetics based on a
"binary-digit" system. This is a pretty similar concept,
although it is certainly implemented differently on each system.
The group of sounds that the human perceptual system tags as
having"the same pitch" is so complicated and weird that any
pitch-analysis algorithm with relevance to the human listener must
essentially be isomorphic to the human processing ability. The same is
true for any other perceptual features like loudness, tempo, chord
When two instruments are playing notes from the same chord (particularly
octave or fifth intervals) they will share some harmonics which makes
segregation more difficult. It can also give the effect of a `harmonic
root' an octave or so below, which is a kind of virtual pitch phenomenon
(e.g. you can hear a low note even when there is no fundamental).
So the engineering problem is very difficult. Even the most raw signal
processing approaches to the problem are doomed to fail because they do
not incorporate information about the structure inherent to musical
signals. There is structure on many different levels, from the low level
sinusoidal/harmonic model, through Gestalt grouping, high time domain
correlations (eg pitch varies slowly over time), and also much higher
levels of modelling which incorporate elements of music theory.
As a result of six years, Innovative Music Systems (IMS) pretends creating
the ultimate polyphonic technology for MP3 to MIDI and WAVE to MIDI
conversion. IntelliScore for PC - for Mac only via Virtual PC -
(look at http://www.intelliscore.net) converts MP3 tracks to MIDI and
audio tracks (WAVE format) to MIDI -files. IntelliScore also allows to
assign notes to different filters (='patches' like classical full
orchestra, choir, Indian raga etc.) based on their pitch. These features
allow to control the conversion process and save editing time.
If you have any experience in this matter of polyphonic pitch recognition,
I strongly invite you to mail me.
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