In 12-tone music, how frequently do composers allow themselves to alternate between adjacent notes of the tone row?

Question

In Vi Hart's [video](https://www.youtube.com/watch?v=4niz8TfY794) on twelve-tone nursery rhymes, she says that one of the rules of twelve-tone composition is that you're allowed to alternate between adjacent notes in the tone row as much as you want; you're just never allowed to jump back by two notes. For example, if the beginning of your tone row was C#-G-Ab-E-C-..., you could write a melody that began C#-G-Ab-G-Ab-E, but not one that began C#-G-Ab-C#-G.My knowledge of the subject is pretty limited, but I'd never heard of this rule before, and it doesn't seem to happen in any of the examples on [this Wikipedia page](http://en.wikipedia.org/wiki/Twelve-tone_technique) (or be stated as a rule there).**How common is this kind of alternation in 12-tone music?** Is it universally considered legitimate, or do only some composers allow themselves to do it (or is it just an error)?

Answer 1

Typically, the rule with twelve-tone music is that once you have used a note in your tone row, you are unable to use it again until you have used the 11 other notes. In essence, you are creating a twelve-note melody, and once you have incorporated all twelve chromatic notes, you can develop them and reuse notes. I want to point out, however, that this rule is broken ALL THE TIME by well-respected composers, including Schoenberg, who developed the twelve-tone method. Writing tone rows can be a great deal of fun and a good composition practice, but never feel too constrained about rules- music should never be about the rules.