Four “Unfinished Masterpieces” by Mendelssohn, Schubert, and Mozart added up to a meaty evening of fine singing and playing by the Back Bay Chorale and Orchestra under Scott Allen Jarrett on Saturday in Jordan Hall.

According to the German archaeologist and Mozart biographer Otto Jahn (cited in Mendelssohn by R. Larry Todd), Mendelssohn intended his third oratorio, originally called Earth, Heaven, and Hell, to complement his Elijah. A keen admirer of Handel’s oratorios as well as Bach’s Passions, Mendelssohn used the precedent of Messiah, in which a series of Old Testament prophecies are fulfilled in the Gospels, shaping his libretto to underscore parallels between Elijah and Christ. The surviving movements depict the birth and passion of Christ; subsequent sections were planned for the Resurrection and the Last Judgment. Mendelssohn played parts of the first section for Queen Victoria in May 1847, but on November 4^th of the same year he died, leaving the work unfinished. His brother Paul collected the surviving fragments and gave them the name Christus, published in 1852 as Opus 97. Part I opened with a solemn accompanied recitative, sung with ringing clarity by soprano Amanda Forsythe as narrator, announcing the coming of the wise men from the east in search of the newborn Christ. In the smoothly homophonic trio that followed, the magi were represented by the men’s voices of the chorus rather than by soloists. A massive Handelian chorus with full orchestra, including trombones and timpani, followed with the crucial text: “Es wird ein Stern aus Jacob aufgeh’n” (A star will arise out of Jacob). Balaam’s Third Oracle (from Numbers 24) prophesies the rise of King David but can also be interpreted as a reference to the Messiah and the Star of Bethlehem; the insertion of the text and melody of the well-known chorale “Wie schön leuchtet der Morgenstern” (How beautifully shines the Morning Star) at the end of the chorus makes the potential link between Old and New Testaments clear.

In Part II on the Trial and Passion of Christ, the excellent tenor Lawrence Jones took on the roles of both traditional narrator and Pilate, with the chorus as discordant and finally repentant crowd. Mendelssohn, however, had removed those passages in the gospels of Luke and John that hold the Jews responsible for the crucifixion, upholding the Lutheran tradition of universal blame for sin. Jones’s high, clear delivery maintained its calm in opposition to increasingly impassioned outbursts from the crowd, recalling similar scenes in Bach’s Passions. The choral response to the narrator’s first recitative was itself a recitative, first by the entire chorus, then in short exclamations exchanged between male and female voices. The second response to Pilate, more legalistic, began as a pompous fugue and ended in block chords. Dramatic tension built up in increasingly urgent responses, their effect heightened by excellent diction. In a lyrical outpouring of mourning, the Daughters of Zion voiced their despair. The final movement again presented a Lutheran chorale: two stanzas of “O Welt sieh’ hier dein Leben” (O world, see here thy life), which appears in both the St. Matthew and the St. John Passions, underscoring Mendelssohn’s indebtedness to Bach.

Mendelssohn composed his Nunc dimittis for four-voice a cappella choir and four soloists in June 1847 while mourning the death of his sister Fanny. The text, from the Gospel of Luke, commemorates the encounter in the temple in Jerusalem between the infant Jesus and the old man Simeon, who blessed him as “a light to lighten the Gentiles and to be the glory of thy people Israel.” After an imitative opening, the four parts proceeded in smoothly conjunct lines. In a short solo section, Forsythe and Jones were joined by alto Margaret Lias and bass Woodrow Bynum. Scott Allen Jarrett’s appropriately restrained orchestration allowed the vocal polyphony to soar.

Franz Schubert broke off the composition of his B Minor Symphony after completing only the first two movements and a fragment of a Scherzo, yet the two finished movements stand on their own in demonstrating an entirely new and genial orchestral language. Instead of grabbing our attention with a forceful downbeat, the first movement famously builds up its opening stealthily, from a low-pitched, modally and rhythmically indeterminate growl, pianissimo, in cellos and basses to time-marking pizzicato in the lower strings, tremolo in the violins and, finally, a plaintive melody emerging from above in the special timbre of unison oboes and clarinets, punctuated by a horn call in the bassoons and horns. A correspondingly hesitant path blurs the entry of the lyrical second theme in the cellos, leading down from the first emphatic cadence on B Minor to a tentative G Major by way of an ambiguous single pitch. These are magical moments that Jarrett and the Back Bay players did not quite pull off, sounding ragged and uncertain rather than uncannily mysterious. In the rhythmically intense development section they were more convincing: crashing tutti dissonances and merciless blasts from brasses and timpani contrasted with an eerily pianissimo preparation for the return and the nostalgic postscript of the coda. In the second movement Andante con moto, Jarrett found just the right tempo that never dragged yet allowed the many exquisite details of orchestration and figuration to come to the fore.

Mozart was still working on his Requiem when he died. Only the Introit “Requiem aeternam” was substantially complete. For the Kyrie, the long Sequence in several parts, and the Offertory he left drafts that included the voice parts, the bass line, and hints of the orchestration. The Lacrimosa (the final stanza of the Sequence) breaks off after only eight measures, and the final movements (Sanctus, Benedictus, Agnus Dei, Lux aeterna, and Cum sanctis tuis) were not even begun. His assistant Franz Xaver Süssmayr completed the orchestration from the drafts, finished the Lacrimosa, and composed the Sanctus and Benedictus. To set the texts of the final movements, he simply adapted Mozart’s music from earlier portions of the Requiem. Although there have been many attempts to complete the Requiem in recent decades, it was Süssmayr’s version, edited by Johannes Brahms, that was published in the Complete Edition of Mozart’s works in the 1870s and that has survived in many modern editions, including, I believe, that used by the Back Bay Chorale in this performance.

The Back Bay Chorale numbers well over 100 singers, a sizable group to coordinate in music as varied and as many layered as Mozart’s Requiem. Thanks to Scott Jarrett’s incisive direction (and, one can be sure, productive rehearsal techniques) they sang confidently with pleasing tone and precise diction. Placing the four soloists behind the orchestra and directly in front of the chorus as though they simply emerged from the tutti group was a good idea that brought increased focus to the many salient wind parts. Jarrett’s tempo for the Introit (Adagio) seemed a bit ponderous, in contrast to the fast Kyrie with its breakneck Christe countersubject that left the sopranos struggling to keep up. Percussive declamation set the tone in the “Dies irae” (Day of wrath). “Tuba mirum” began with a virtuosic dialogue between tenor trombonist Wes Hopper and bass soloist Woodrow Bynum, followed by stanzas for tenor, alto, and soprano solo, with all four singers on the quiet concluding line. The dotted rhythms and jagged intervals of “Rex tremendae majestatis” (King of terrifying majesty) gave way to a brief plea for mercy, followed by the smoothly flowing counterpoint of “Recordare , Jesu pie” (Remember, merciful Jesus) in a beautifully matched ensemble of the four soloists. A stern “Confutatis maledictis” (When the accursed are confounded) led to the gentle “Lacrimosa dies illa” (O how tearful that day). Mozart supplied the voices and continuo parts for the first section of the Offertory, “Domine Jesu Christe” (Lord Jesus Christ). The homophonic opening sections of the chorus were dramatically effective, even though angular fugue subjects on “ne absorbeat” and “quam olim Abrahae” tended to get lost at the ends of phrases; mellifluous counterpoint from the solo quartet on “Sed signifier sanctus Michael . . .” (But let Michael, the holy standard-bearer . . .) introduced yet another textural contrast.

After the peaceful interlude of the “Hostias et preces tibi” (Sacrifices and prayers to Thee), and the repetition of the “Quam olim Abrahae” fugue, the chorus launched full force into Süssmayr’s grand Sanctus, the orchestra now augmented by trumpets and timpani. The extended Benedictus, beautifully rendered by the vocal soloists, brought an interlude of calm before the dramatic Agnus Dei. Whether or not that had been Mozart’s original intention, Süssmayr rounded off the Requiem by bringing back sections of the opening Introit and Kyrie, now set to the words of the Communio: “Lux aeterna lucet eis . . . quia pius es” (May light eternal shine upon them . . . for thou art merciful).

It takes a large measure of dedication and skill for a big volunteer organization like the Back Bay Chorale to put together the ambitious program we heard on Saturday. Their joy in performance obviously trumps whatever “real life” commitments they may have, bringing them together for the rigorous preparation needed to make real music. Conductor Scott Allen Jarrett has shaped the group into a flexible ensemble with fine tone quality and expressive power. Centered around unfinished works, and juxtaposing well-known with lesser-known pieces, Saturday’s program placed familiar favorites in a new historical context.

Virginia Newes, who lives in Cambridge, was Associate Professor of Music History and Musicology at the Eastman School of Music.