Universally acknowledged as one of the greatest pieces of choral music, JS Bach's Mass in B Minor is also one of the most challenging for any choral society.

JS Bach

Johann Sebastian Bach (1685–1750) was a German musician and composer. He came from a musical family and initially earned a living as an organist. He worked in a number of different musical positions around Germany which involved playing, directing and composing music, eventually settling in Leipzig where he was the Cantor (director of music) at the Thomasschule (St Thomas School), a post which gave him responsibility for the music in many of the churches of the city. He remained in that position for 27 years, until his death.

Bach was a mean keyboard player, excelling at both organ and harpsichord (pianos had yet to be invented). He liked to enter keyboard-playing competitions but was so successful that he used to attend them in disguise so as not to discourage the other competitors. He had an amazing ability to improvise, and on one occasion improvised a three-part fugue based on a theme played to him by Frederick, the King of Prussia.

Throughout his life Bach wrote music for whatever the situation demanded. His orchestral music is for the instruments that happened to be available in the orchestra he was working in. When employed by the Calvinist Leopold of Anhalt-Köthen, whose religion did not encourage music in church, he wrote secular music including the Cello Suites, the celebrated 'Air on a G String' and the Brandenburg Concertos.

Mostly, though, Bach wrote sacred music for performance at religious services. He churned the stuff out, often by re-using earlier works and modifying them. It has been estimated that if a modern copyist were to write out Bach's complete works by hand, a single lifetime would not be enough to set them all down. Bach was a Lutheran and the form he specialised in was the Cantata, a collection of short sung pieces on a religious theme with orchestral accompaniment, each Cantata making up about 30 minutes of music. He wrote over 300 of these and they were performed in churches in Leipzig on Sundays and religious holidays.

Bach was married twice and had 20 children, of whom only 10 survived to adulthood. A number of his sons became composers themselves, including Wilhelm Friedemann, Carl Philipp Emanuel, Johann Christoph Friedrich and Johann Christian.

After his death, Bach was remembered more as a talented organist than a composer. His compositions were considered old-fashioned, hearkening back to the age of polyphony and fugue. It was only in the 19th Century that interest in Bach's music revived and he became recognised as one of the greatest of composers.

The Mass in B Minor

Towards the end of his life, Bach assembled a number of his earlier compositions together, rewriting them, shaping them and adding extra sections to make the work which is now known as the Mass in B Minor. The sung mass is a feature of the Roman Catholic rite - five of the prayers of the mass are set to music and sung during the religious service. This had been done for centuries, with such famous composers as Palestrina, Victoria and Byrd. Why a devout Lutheran like Bach would want to write such a work is a bit of a mystery. It was never performed during his lifetime and there's no record of anybody commissioning it. It seems to have been just a private project in which he collected the best bits of his life's work and put them together to make a grand work.

And it is indeed grand, containing some of the finest choral music ever written. Bach never gave it a title. His son Carl Philipp Emanuel, who inherited the score, called it the Great Catholic Mass. The name Mass in B Minor comes from the key signature of the first movement, and while some of the other movements are also in this key, there are plenty of other keys used throughout the work. The Mass in B Minor was first performed in 1859, more than a century after his death. If it was Bach's intention to make a showcase of his greatest music, then he succeeded in producing something which will keep the memory of his name alive.

The Mass is mainly written for chorus divided into five voice types, with bass, tenor, alto and two sopranos. There are other combinations of voices used in some movements. In addition, Bach wrote for five solo voices, one in each voice range.

Much of the Mass is written in a style called 'fugue', which literally means 'chase'. Instead of all the voices singing the same thing at the same time, one voice starts singing first, the second voice comes in after a delay with the same tune, and the others follow in turn. We hear the same theme occurring again and again, sung by different voices. Of course to make it all fit together, some clever techniques are needed such as changing the key, or modifying the tune slightly to get it to fit. Bach was a master of fugue and went somewhat overboard on it in the Mass in B Minor.

In Performance

The Mass in B Minor is normally performed in a concert setting, with an audience - not as part of an actual liturgical mass.

Modern-day performances tend to run to about 110 minutes, not including any intervals. Recordings from the mid-20th Century are much longer, as conductors took the Mass at a much more leisurely pace. Klemperer's 1968 recording, for example, is 136 minutes.

It is usual to put an interval between the Gloria section and the Credo. This divides the Mass into two roughly equal portions.

In many performances, the second soprano solo part is performed by the soprano or alto soloist as appropriate, to reduce the number and hence cost of soloists.

A Detailed Analysis

As is normal in sung masses, there are five main sections:

• Kyrie (Lord have mercy)
• Gloria (Glory to God)
• Credo (I believe in one God)
• Sanctus (Holy holy)
• Agnus Dei (Lamb of God)

Bach produced such an elaborate setting of the Mass that he split each of these up into a number of separate movements.

Kyrie

Bach divided this section into three separate movements, with the choir taking the outer Kyrie movements and two soloists performing the Christe movement as a duet.

1. Chorus: Kyrie eleison

The Mass starts with a bold statement by the choir. The orchestra then introduces the main theme of the first part. It is in the form of a fugue, where the same theme gets played by different instruments at different times, all weaving together. The fugue is then taken up by the choir, starting with the tenors and gradually introducing the other parts. You should be able to hear the same opening phrase reappearing again and again, sung by different voices and in different keys, eventually coming to a final resolution.

2. Duet: Christe eleison

The first and second soprano soloists now take the stage for this second movement. This is a lyrical duet, with the two voices mainly singing the same words at the same time in harmony, but an equally important part of the music is provided by the strings with an insistent, long and elaborate phrase. This contrasts in its complexity with the simplicity of the voices.

3. Chorus: Kyrie eleison

For this second statement of the 'Lord have mercy', Bach provides a completely new fugal theme. This states the word 'Kyrie' on three notes only a semitone apart, leading to a tense and exciting fugue.

Gloria

The Gloria is a song praising God and starting with the angels' song to the shepherds at the birth of Christ. Bach divides this into nine separate movements.

1. Chorus: Gloria in excelsis

There's nothing quite as glorious and exuberant as a trumpet. This movement has three of them, in a jolly tune. After an instrumental introduction the choir launches into a fugue, starting this time with the altos. This leads directly into the next movement.

2. Chorus: Et in terra pax

There’s a sudden change of style, to signify peace. A smooth, lyrical section proclaims 'and peace on Earth'. After a short orchestral interlude, the sopranos start another fugue. This one introduces the infamous Bach semiquavers – these are sequences of very rapid notes which are lyrical but very difficult to sing, making the Mass in B Minor one of the most challenging works, in terms of physical effort as well as the sheer number of notes. There are a lot of semiquavers!

As the movement progresses, the trumpets join back in for a triumphant flourish at the end.

3. Soprano II Solo: Laudamus te

This is an elaborate duet between the Second Soprano and the First Violin.

4. Chorus: Gratias agimus tibi

This slow and solemn fugue gradually builds into a massive statement of thanks as the voices rise in pitch and become more and more insistent, being joined by more and more instruments.

5. Duet: Domine Deus

This is a duet between the First Soprano soloist and the Tenor, but the two parts sing together against a background of an elaborate flute tune in a style called 'obbligato'. Bach was fond of this form; he often gave the instrument a far more demanding part than the singers. In fact Bach never specified in the score what instrument was to play the obbligato part in this movement – in some versions the tune is given to the First Violin.

6. Chorus: Qui tollis peccata mundi

As befits a plea for mercy, this chorus is slow and solemn. Once again it is a fugue, and features a long held note on the syllable 'ca' of 'peccata', which clashes each time with the next chord, producing a succession of tensions followed by resolutions.

7. Alto Solo: Qui sedes ad dextram Patris

This alto solo is once again presented in the obbligato style with the singer's melody placed against an elaborate counter-melody. This time, the instrument is the rare oboe d'amore. This big sister of the oboe has a deeper and rounder tone, playing a minor third lower.

8. Bass Solo: Quoniam tu solus sanctus

Another solo with an elaborate obbligato part, this time for bass voice and a hunting horn, accompanied by two bassoons. This is the only movement in the whole work that uses the horn. It leads straight into the next movement.

9. Chorus: Cum Sancto Spiritu

This movement is one of the most exciting and technically difficult in the whole work. There are parts where the four upper voices sing massive chords while the basses jump about in arpeggios. There are rapid semiquaver passages. There are trumpets! Mozart was once accused of using 'too many notes'. What would that critic have made of Bach? This jolly and breathtaking romp brings the Gloria section to a close.

Credo

The Credo is a statement of belief, established at the Council of Nicaea, to define what Christians believe in. It is a difficult text to set to music as it has so many words. Bach divides it into nine movements.

1. Chorus: Credo in unum Deum

The first movement of the Credo is a fugue. The theme of the fugue, stated first by the tenors, is a phrase of Gregorian chant which has been used for centuries for the start of the Credo. Bach often starts simply, but rarely remains so. You'll hear this phrase being passed around from one voice section to the next. He even gets the basses to sing the theme at half speed near the end of the movement, although this is not easy to pick out from the complex texture.

2. Chorus: Patrem omnipotentem

This movement deals with God the Father. A fugue for four voice parts is joined by trumpets unobtrusively providing embellishments above all the singers.

3. Duet: Et in unum dominum

This movement is the first of three that deal with Jesus Christ. It is a duet between First Soprano and Alto. In much of it, the alto sings the same or similar music to the soprano but just one beat after her. Bach manages to get through a lot of the text of the Credo in this movement by avoiding his normal repetition.

4. Chorus: Et incarnatus est

The words 'et incarnatus' are set to a descending theme to represent Christ coming down from heaven to become a man. This is a slow and solemn movement, representing musically the tradition of pausing and bowing one's head to mark Christ's incarnation.

5. Chorus: Crucifixus

The Credo is the central section of the Mass, and this movement is the central one of the Credo. This is the central point of the Mass in B Minor, and it is fitting that it should tell of Christ's death on the cross: Lutherans hold this to be the most important part of Christianity. The music represents the solemnity and sadness with dissonances and constantly changing chords against a repeated downward-moving bass phrase in the orchestra. The movement ends as Christ is buried with all the voices singing at the bottom of their range, although there is an unexpected twist at the very end as it shifts into a new key to prepare for the next movement.

6. Chorus: Et resurrexit

This movement explodes into life without any introduction, telling the joyous news that Christ rose from the dead. The trumpets join in to make a vivacious affirmation of the resurrection. The rest of the movement proceeds with fugues, musical interludes and a short bass solo. Near the end, the sopranos illustrate the phrase 'his kingdom will never end' with an extended phrase of six bars on the single word 'regni' (kingdom). The movement ends with an orchestral play-out.

7. Bass Solo: Et in Spiritum sanctum Dominum

The bass soloist tells of the Holy Spirit and the Church, with an obbligato part for two oboes d'amore.

8. Chorus: Confiteor

The choir sings an extended fugue. There is a sudden slowing down and the mood changes:

A slow section follows with strained chords full of suspended notes and dissonant clashes, giving a sense of something unusual about to happen.

9. Chorus: Et expecto

The mood changes again to exuberance and life as the trumpets join in. The whole Credo section is rounded off with a demanding and rapid fugue.

Sanctus

The Sanctus is a hymn of praise to God.

1. Chorus: Sanctus

This movement was written for a Christmas celebration. The words are those spoken by the seraphim (a type of angel) in a vision of the prophet Isaiah. It is scored for six parts, with First and Second sopranos, First and Second altos, tenors and basses. The first section has some voices declaiming 'Sanctus' as others sing an undulating accompaniment in triplets. Then the top voices sing massive chords as the basses sing a marching line jumping up and down in octaves. This leads straight into a fugue on 'pleni sunt coeli', with long semiquaver runs on the word 'gloria'.

2. Chorus: Osanna in excelsis

The words of this section and the next were shouted by the crowd as Jesus came in triumph into Jerusalem. This movement is for two choirs, each with soprano, alto, tenor and bass. Ideally the two choirs should be positioned on either side of the performance space, as Bach introduces some interesting effects such as the first choir singing and the second choir accompanying and then the other way around. Practical considerations, however, prevent this from being done in most performances. The movement is once again a fugue with semiquaver runs, with an orchestral play-out.

3. Tenor Solo: Benedictus

Amid all the triumph, we now have a peaceful tenor solo movement with a beautiful flute obbligato part.

4. Chorus: Osanna in excelsis

This movement is an exact repeat of the second movement of the Sanctus.

Agnus Dei

The Agnus Dei prayer addresses Jesus Christ three times, calling him the Lamb of God. The symbol of Jesus as a Lamb was provided by John the Baptist at Jesus's baptism. It calls to mind the Paschal lamb of the Jewish passover; by killing a lamb, the Jews gave a sign to God that they would obey his instructions and so were saved from God's wrath. In the same way, the Lamb of God by dying saves all mankind from eternal punishment.

The first two times the prayer calls upon the Lamb of God, it says 'have mercy on us'. The third time, the request is 'give us peace'. Bach combined the first two into a single movement, writing the 'give us peace' as a separate movement.

1. Alto Solo: Agnus Dei

This alto solo features a prominent obbligato violin part. The alto has some beautiful phrases with long held notes.

2. Chorus: Dona nobis pacem

To conclude the Mass, Bach chose to re-use the music for the movement 'Gratias agimus tibi'. There's a symmetry to this - the first time it is used, the choir thanks God for His help; the second time, they ask Him for His help. The melodies sung by the choir are changed very slightly to fit the new words but other than that, this is identical to the Gratias movement. Again there is the slow build up to the glorious finale. The trumpets ring out and bring Bach's greatest work to a dramatic conclusion.