Inversion

In musical theory an inversion is to write one or more notes of a chord an octave above its natural position.

For example, the root position of a triad of C major is:

http://meta.wikipedia.com/upload/c_triad.png

The first inversion means to shift the bottom note (the C) an octave higher:

http://meta.wikipedia.com/upload/inv2.png

The second inversion is to write the E an octave above:

http://meta.wikipedia.com/upload/inv3.png

The third inversion of a triad cannot be constructed, since shifting the G an octave higher would simply form the original root triad up an octave:

http://meta.wikipedia.com/upload/inv4.png

It is, however, possible to find the third inversion of chords which have four notes or more, such as the dominant seventh.

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An Inversion is a meteorological phenomenon where (?cold air gets trapped above warm?), preventing air circulation. When inversions occur, air quality suffers.