▁oct aves , ▁avoid ance ▁of ▁traditional ▁pitch ▁collections ▁such ▁as ▁major ▁or ▁minor ▁tri ads , ▁avoid ance ▁of ▁more ▁than ▁three ▁success ive ▁pitch es ▁from ▁the ▁same ▁di at onic ▁scale , ▁and ▁use ▁of ▁dis j unct ▁mel od ies ▁( av oid ance ▁of ▁conj unct ▁mel od ies ) ▁. ▁ ▁Further , ▁Per le ▁agre es ▁with ▁ ▁and ▁ ▁that , ▁" the ▁abandon ment ▁of ▁the ▁concept ▁of ▁a ▁root - generator ▁of ▁the ▁individual ▁ch ord ▁is ▁a ▁radical ▁development ▁that ▁rend ers ▁fut ile ▁any ▁attempt ▁at ▁a ▁system atic ▁form ulation ▁of ▁ch ord ▁structure ▁and ▁pro gression ▁in ▁at onal ▁music ▁along ▁the ▁lines ▁of ▁traditional ▁harm onic ▁theory " ▁. ▁A ton al ▁compos itional ▁techniques ▁and ▁results ▁" are ▁not ▁redu cible ▁to ▁a ▁set ▁of ▁found ational ▁assumptions ▁in ▁terms ▁of ▁which ▁the ▁compos itions ▁that ▁are ▁collect ively ▁designated ▁by ▁the ▁expression ▁' at onal ▁music ' ▁can ▁be ▁said ▁to ▁represent ▁' a ▁system ' ▁of ▁composition " ▁. ▁Equ al - interval ▁ch ords ▁are ▁often ▁of ▁ind et erm inate ▁root , ▁mixed - interval ▁ch ords ▁are ▁often ▁best ▁character ized ▁by ▁their ▁interval ▁content , ▁while ▁both ▁l end ▁themselves ▁to ▁at onal ▁context s ▁. ▁ ▁Per le ▁also ▁points ▁out ▁that ▁struct ural ▁coh er ence ▁is ▁most ▁often ▁achieved ▁through ▁operations ▁on ▁inter v all ic ▁cells . ▁A ▁cell ▁" may ▁operate ▁as ▁a ▁kind ▁of ▁micro