▁a ▁sin f onia ▁and ▁then ▁altern ates ▁ch oral ▁movements ▁and ▁a rias . ▁There ▁are ▁no ▁rec it atives , ▁no ▁da ▁cap o ▁repe ats , ▁and ▁there ▁is ▁no ▁ch or ale ▁t une , ▁unus ually ▁for ▁Bach ' s ▁cant at as . ▁Bach ▁makes ▁extensive ▁use ▁of ▁ch oral ▁fug ues ▁and ▁im itative ▁poly phony , ▁often ▁sh ifting ▁the ▁tempo ▁and ▁character ▁of ▁the ▁music ▁within ▁movements ▁very ▁quickly ▁to ▁accommod ate ▁a ▁new ▁musical ▁idea ▁with ▁each ▁success ive ▁phrase ▁of ▁text . ▁ ▁The ▁sin f onia ▁and ▁the ▁opening ▁ch oral ▁movement ▁are ▁both ▁based ▁on ▁the ▁mot ive ▁of ▁an ▁oct ave ▁le ap ▁followed ▁by ▁five ▁desc ending ▁half ▁steps . ▁This ▁chrom atic ▁figure , ▁sometimes ▁dub bed ▁the ▁" l amento ▁bass " ▁or ▁pass us ▁dur ius cul us , ▁has ▁been ▁util ized ▁by ▁compos ers ▁as ▁early ▁as ▁Monte ver di ▁as ▁a ▁musical ▁representation ▁of ▁an gu ish , ▁pain , ▁and ▁long ing . ▁The ▁sin f onia ▁also ▁introdu ces ▁them atic ▁material ▁developed ▁later ▁in ▁the ▁work , ▁uses ▁asym metric ▁phr asing , ▁and ▁" a ▁se am less ▁flow ▁of ▁un sto pp able ▁mel ody ". ▁ ▁The ▁first ▁ch orus ▁on ▁the ▁beginning ▁of ▁Ps alm ▁ 2 5 , ▁"" ▁( L ord , ▁I ▁long ▁for ▁you . ▁My ▁God , ▁I ▁hope ▁in ▁you .), ▁is ▁" way ward ly ▁constructed ▁despite ▁its