Polyeleos
...that Psalms 134 and 135 are usually chanted during the Polyeleos, a festive portion of the Matins or All-night vigil services in some Eastern Christian Churches, but Psalm 44 is chanted instead on feasts of the Theotokos in Greece?
...that <a href="./Psalms" id="mwAnc" rel="mw:WikiLink" title="Psalms">Psalms</a> 134 and 135 are usually chanted during the <b id="mwAng"><a href="./Polyeleos" id="mwAnk" rel="mw:WikiLink" title="Polyeleos">Polyeleos</a></b>, a festive portion of the <a href="./Matins" id="mwAno" rel="mw:WikiLink" title="Matins">Matins</a> or <a href="./All-night_vigil" id="mwAns" rel="mw:WikiLink" title="All-night vigil">All-night vigil</a> services in some <a href="./Eastern_Christianity" id="mwAnw" rel="mw:WikiLink" title="Eastern Christianity">Eastern Christian Churches</a>, but Psalm 44 is chanted instead on <a href="./Calendar_of_saints" id="mwAn0" rel="mw:WikiLink" title="Calendar of saints">feasts</a> of the <a href="./Theotokos" id="mwAn4" rel="mw:WikiLink" title="Theotokos">Theotokos</a> in <a href="./Church_of_Greece" id="mwAn8" rel="mw:WikiLink" title="Church of Greece">Greece</a>?