Z-relation
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In musical set theory, a Z-relation is a relation between two sets in which the two sets have the same intervallic content (i.e. they have the same interval vector), but they are of different Tn-type and Tn/TnI-type. That is to say, one set cannot be derived from the other though transposition or inversion.
For example, the two sets {0,1,4,6} and {0,1,3,7} have the same interval vector (<1,1,1,1,1,1>) but they are not transpositionally or inversionally related.
The term originated with Allen Forte, in his Structure of Atonal Music (ISBN 0300021208).
Some argue that the "relation" is so remote as to be imperceptible, but certain composers have exploited the Z-relation in their work.Template:Music-theory-stub