▁d ode cap h onic ▁purposes ▁a ▁per vas ive ▁technical ▁feature ▁of ▁' mod ern ' ▁musical ▁practice , ▁the ▁ost in ato " ▁ ▁Compos ing ▁at onal ▁music ▁Setting ▁out ▁to ▁compose ▁at onal ▁music ▁may ▁seem ▁complicated ▁because ▁of ▁both ▁the ▁v ag uen ess ▁and ▁general ity ▁of ▁the ▁term . ▁▁ ▁Additionally ▁George ▁Per le ▁explains ▁that , ▁" the ▁' free ' ▁at on ality ▁that ▁preced ed ▁d ode cap h ony ▁pre cludes ▁by ▁definition ▁the ▁possibility ▁of ▁self - cons istent , ▁generally ▁applicable ▁compos itional ▁procedures " ▁. ▁However , ▁he ▁provides ▁one ▁example ▁as ▁a ▁way ▁to ▁compose ▁at onal ▁pieces , ▁a ▁pre - tw elve - t one ▁technique ▁piece ▁by ▁Anton ▁We bern , ▁which ▁rig or ously ▁avoid s ▁anything ▁that ▁suggests ▁ton ality , ▁to ▁choose ▁pitch es ▁that ▁do ▁not ▁imply ▁ton ality . ▁In ▁other ▁words , ▁reverse ▁the ▁rules ▁of ▁the ▁common ▁practice ▁period ▁so ▁that ▁what ▁was ▁not ▁allowed ▁is ▁required ▁and ▁what ▁was ▁required ▁is ▁not ▁allowed . ▁This ▁is ▁what ▁was ▁done ▁by ▁Charles ▁Se eg er ▁in ▁his ▁explanation ▁of ▁dis son ant ▁counter point , ▁which ▁is ▁a ▁way ▁to ▁write ▁at onal ▁counter point ▁. ▁ ▁Kost ka ▁and ▁Pay ne ▁list ▁four ▁procedures ▁as ▁oper ational ▁in ▁the ▁at onal ▁music ▁of ▁Sch o enberg , ▁all ▁of ▁which ▁may ▁be ▁taken ▁as ▁negative ▁rules . ▁A void ance ▁of ▁mel od ic ▁or ▁harm onic