▁lat itudes , ▁so ▁during ▁this ▁season ▁three ▁Kath ism ata ▁will ▁be ▁ch anted ▁at ▁Mat ins ▁instead ▁of ▁two , ▁so ▁in ▁order ▁to ▁still ▁have ▁a ▁reading ▁from ▁the ▁Ps alter ▁at ▁V es pers , ▁the ▁E igh teenth ▁Kath is ma ▁is ▁repeated . ▁ ▁An ab ath mo i ▁ ▁At ▁Mat ins ▁on ▁Sund ays ▁and ▁fe ast ▁days ▁throughout ▁the ▁year , ▁special ▁h ym ns ▁called ▁an ab ath mo i ▁( , ▁from ▁ β α θ μ ό ς , ▁' step '; ▁S lav onic : ▁step én ny ) ▁are ▁ch anted ▁immediately ▁before ▁the ▁pro ke imen on ▁and ▁Mat ins ▁G ospel . ▁These ▁an ab ath mo i ▁are ▁compos itions ▁based ▁upon ▁the ▁Songs ▁of ▁As c ents , ▁and ▁are ▁written ▁in ▁the ▁eight ▁t ones ▁of ▁By z antine ▁chant . ▁The ▁An ab ath mo i ▁for ▁each ▁tone ▁consists ▁of ▁three ▁st ases ▁or ▁sets ▁of ▁vers es ▁( s ometimes ▁called ▁anti ph ons ), ▁except ▁for ▁T one ▁ 8 ▁which ▁has ▁four ▁st ases . ▁On ▁Sund ays , ▁the ▁an ab ath mo i ▁are ▁ch anted ▁according ▁to ▁the ▁tone ▁of ▁the ▁week ; ▁on ▁fe ast ▁days ▁which ▁do ▁not ▁fall ▁on ▁Sunday , ▁the ▁An ab ath mo i ▁almost ▁always ▁consist ▁of ▁the ▁first ▁st asis ▁in ▁T one ▁ 4 ▁( based ▁on ▁Ps alm ▁ 1 2 8 ). ▁ ▁Symbol ically