▁commonly ▁used ▁ch ants ▁are ▁double ▁ch ants . ▁These ▁are ▁twice ▁the ▁length ▁of ▁a ▁single ▁chant . ▁The ▁music ▁of ▁the ▁chant ▁is ▁repeated ▁for ▁every ▁pair ▁of ▁vers es . ▁This ▁reflect s ▁the ▁structure ▁of ▁the ▁Heb rew ▁poetry ▁of ▁many ▁of ▁the ▁ps al ms : ▁Each ▁verse ▁is ▁in ▁two ▁hal ves ▁– ▁the ▁second ▁half ▁answers ▁the ▁first ; ▁the ▁vers es ▁are ▁in ▁pairs ▁– ▁the ▁second ▁verse ▁answers ▁the ▁first . ▁ ▁Tri ple ▁and ▁quad ru ple ▁ch ants ▁are ▁consider ably ▁r ar er . ▁They ▁appeared ▁from ▁the ▁latter ▁part ▁of ▁the ▁ 1 9 th ▁century ▁to ▁cover ▁some ▁of ▁the ▁exceptions ▁to ▁this ▁format . ▁They ▁set ▁the ▁vers es ▁of ▁the ▁ps alm ▁in ▁groups ▁of ▁three ▁or ▁four ▁vers es ▁respectively . ▁Ps alm ▁ 2 ▁( for ▁example ) ▁is ▁su ited ▁to ▁a ▁triple ▁chant ; ▁a ▁quad ru ple ▁chant ▁might ▁be ▁used ▁for ▁Ps alm ▁ 7 8 . ▁ ▁A ▁double ▁chant ▁is ▁divided ▁into ▁" quarters ", ▁each ▁of ▁which ▁has ▁the ▁music ▁for ▁half ▁a ▁verse . ▁Tri ple ▁and ▁quad ru ple ▁ch ants ▁may ▁also ▁be ▁described ▁as ▁containing ▁six ▁or ▁eight ▁qu arters . ▁ ▁If ▁the ▁entire ▁text ▁( or ▁a ▁section ▁of ▁it ) ▁has ▁an ▁odd ▁number ▁of ▁vers es , ▁the ▁second ▁half ▁of ▁the ▁chant ▁is ▁usually ▁repeated ▁at ▁an ▁appropriate ▁point , ▁which ▁may ▁be ▁marked ▁" 2 nd ▁part ".