# Theory help



## Interested (Apr 12, 2007)

Hi,

Newbie and first post.....I have a query that I hope someone here may be able to shed some light on.

I seem to remember several years ago seeing a tv show about a musician or about music in general. In it they showed an orchastra with the first violins playing their part alone. Then the second violins played their piece alone. You heard two distinct melodies. Then they both bplayed their parts together and the final melody was a different thing again. Am I imagining this or is this part of music theory.

It seems logical in that music data compression algorithms work on principle that certain sounds mask others and so they can be removed to allow lossy compresion. Anyway, I'm looking for as much info or direction in to areas where I can read about this and what composers use it the best effect.....also whether quartets or small groups of instruments would function same way.

Thanks for all and any help on this.

G


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## zlya (Apr 9, 2007)

Actually, this isn't technically music theory, it's psychoacoustics!

Psychoacoustics is the study of how we hear music, from the biological functioning of the ear to the electrical firings in the brain to the reported emotional responses.

Most likely, the notes of the two melodies were not masking each other in any physical sense. What changed was your brains definition of a melody--i.e. which notes you listened to and grouped together.

This is called auditory scene analysis. This is what lets you associate a certain group of sounds with a certain thing. For example, imagine you're at a party. It's crowded, lots of people are talking, yet if you chose you can hold a conversation with one person, you can pick out exactly what he's saying. There are thousands of pitches of different frequencies and spectra floating around, yet you can associate a particular group with one spoken line. How do you do that?

Well, a man called Bregman came up with the theory of auditory scene analysis, which says you use several clues such as frequency (sounds closer in pitch might be related) and proximity (sounds coming from the same place might be related). His theory is based on Gestalt grouping principles. Remember those tricky pictures where you can see either a vase or two faces? Same sort of thing.

There's a lot of information on this online, here are some websites:

http://library.thinkquest.org/19537/Ear6.html
http://www.ni.cs.tu-berlin.de/~hendrik/research/asa.html

Also, just typing Auditory Scene Analysis into Google should get you some hits.

Essentially what happened in your case was probably that the composer tricked you into grouping certain notes from the two parts into one melody, so that when they played together you heard a melody that went: 1st 1st 2nd 1st 2nd 2nd or something along those lines.

Hope this was helpful!


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