The most noticeable difference between the two passions is the choir and orchestral size. The St. John passion required the typical size passion orchestra: two flutes, two oboes, bassoon, strings and continuo,* as well as the more traditional viola de gamba, lute, and two viole d'amore. It also included a four-part choir with six concertists, or soloists. However, the forces required for the St. Matthew Passion were huge; it required a double orchestra and a double choir. Along with these forces, it also used a viola da gamba, two recorders, three different kinds of oboes, and an extra soprano chorus to sing the ripieno, or full chorale in the first movement. The amount of people needed to perform the St. Matthew passion was mammoth for the time. It gave Bach the flexibility to create a wide range of emotions for the most passionate week of the year.
The St. Matthew uses a single libretto, or text, while the St. John uses words from a variety of sources. The latter contains a famous passion poem by B.H. Brockes, a libretto by C.H. Postel, and parts of the Gospel of St. Matthew in the part of the Evangelist. In contrast, Bach set the music of the St. Matthew passion to a single libretto, written by Christian Friendrich Henrici (Picander). Critics argue that the single text of the St. Matthew Passion accounts, in part, for its structural and musical unity.
Both passions included numerous recitatives.** They were primarily used for the parts of the Evangelist and Jesus, as well as Peter and Pilate. In these sections, both passions used a simple organ continuo accompaniment, repetitive pitches, and a predominant vocal line. However, the St. Matthew passion used the string section, notably two violins and a viola, when Jesus spoke. The accompaniment, described in New Groves as a "halo" was only modest, but it highlighted the lines of Jesus as the most important. Furthermore, the recitatives in the St. Matthew Passion seemed more developed. They were generally longer and included more dialogue between the main characters. The recitatives in the St. John passion, some lasting no more than a measure (nos. 23, 31) were continually interrupted by choral sections. Though this was, at times, beautiful, it hurt the flow of the passion. Therefore, the recitatives in both passions were similar in function but varied in structure, accompaniment, and length.
The arias*** in the two passions differed in many ways. The arias in the St. Matthew were more brilliant and expressive. They incorporated dazzling lines, especially brilliant runs imitated in the instruments. At the same time, the rhythm in the later passion was less metrical. Some arias in the St. John, especially those in the beginning, appeared almost modal, using consistent patterns of long and short notes in the accompaniment, especially the continuo line. Furthermore, the instrumental line played a larger role in the arias of the St. Matthew. Though I listened to the same group for both pieces (John Eliot Gardiner, the Monteverdi Choir, and the London Oratory Junior Choir), the aria accompaniment for the St. Matthew passion was much louder. This made the climaxes dramatic and the vocal line, atop a flurry of instrumentation, more impressive. Therefore, the arias in the St. Matthew were more expressive and less metrical than those in the St. John.
Bach used the most popular Lutheran tradition of the time, the chorale, in both passions. The St. John Passion includes eleven chorales while the St. Matthew uses fifteen. In both passions, the chorales are written for four voice parts, have religious texts, and use an organ continuo accompaniment. Furthermore, the instrumentalists double the vocal lines like this:
Therefore, the chorales are similar in both passions.
Bach's St. Matthew Passion and his earlier St. John Passion share some common musical elements. They both include recitatives, arias, and chorales. While the chorales are very similar, the St. Matthew Passion develops the chorales and arias more. Furthermore, the larger size of the orchestra in the St. Matthew Passion provides a larger range of emotion and the single libretto contributes to a unified structure. Therefore, the St. Matthew Passion is an extension and development of the St. John Passion.