Editing Twelve-tone technique (section)

===Example===
Suppose the prime form of the row is as follows:

:[[Image:Example tone row.png|400px|B, B{{music|b}}, G, C{{music|#}}, E{{music|b}}, C, D, A, F{{music|#}}, E, A{{music|b}}, F]]

Then the retrograde is the prime form in reverse order:

:[[Image:Retrograde tone row.png|400px|F, A{{music|b}}, E, F{{music|#}}, A, D, C, E{{music|b}}, C{{music|#}}, G, B{{music|b}}, B]]

The inversion is the prime form with the [[Interval (music)|intervals]] [[Inversion (interval)|inverted]] (so that a rising [[minor third]] becomes a falling minor third, or equivalently, a rising [[major sixth]]):

:[[Image:Inversion tone row.png|400px|B, C, E{{music|b}}, A, G, B{{music|b}}, A{{music|b}}, C{{music|#}}, E, F{{music|#}}, D, F]]

And the retrograde inversion is the inverted row in retrograde:

:[[Image:Retrograde inversion tone row.png|400px|F, D, F{{music|#}}, E, C{{music|#}}, A{{music|b}}, B{{music|b}}, G, A, E{{music|b}}, C, B]]

P, R, I and RI can each be started on any of the twelve notes of the [[chromatic scale]], meaning that 47 [[permutation (music)|permutations]] of the initial tone row can be used, giving a maximum of 48 possible tone rows. However, not all prime series will yield so many variations because transposed transformations may be identical to each other. This is known as ''invariance''. A simple case is the ascending chromatic scale, the retrograde inversion of which is identical to the prime form, and the retrograde of which is identical to the inversion (thus, only 24 forms of this tone row are available).

[[Image:P-R-I-RI.png|thumb|350px|Prime, retrograde, inverted, and retrograde-inverted forms of the ascending chromatic scale. P and RI are the same (to within transposition), as are R and I.]]

In the above example, as is typical, the retrograde inversion contains three points where the sequence of two pitches are identical to the prime row. Thus the generative power of even the most basic transformations is both unpredictable and inevitable. Motivic development can be driven by such internal consistency.