Ach wie flüchtig, ach wie nichtig, BWV 26

Bach structured the cantata in six movements. The text and tune of the hymn appear unchanged in the outer choral movements, a chorale fantasia and a four-part closing chorale, which frame a sequence of alternating arias and recitatives. Bach scored the work for four vocal soloists (soprano, alto, tenor, bass), a four-part choir and a Baroque instrumental ensemble of a horn (Co) doubling the soprano in the chorale, flauto traverso (Ft), three oboes (Ob), two violins (Vl), viola (Va), organ (Org) and basso continuo.[9]

In the following table of the movements, the scoring follows the Neue Bach-Ausgabe.[9] The keys and time signatures are taken from Alfred Dürr, using the symbol for common time (4/4).[2]

Movements of Ach wie flüchtig, ach wie nichtig

No.	Title	Text	Type	Vocal	Winds	Strings	Others	Key	Time
1	Ach wie flüchtig, ach wie nichtig	Franck	Chorale fantasia	SATB	Co Ft 3Ob	2Vl Va	Org Bc	A minor
2	So schnell ein rauschend Wasser schießt	anon.	Aria	T	Ft	Vl	Org Bc	C major	6/8
3	Die Freude wird zur Traurigkeit	anon.	Recitative	A			Org Bc
4	An irdische Schätze das Herze zu hängen	anon.	Aria	B	3Ob		Org Bc
5	Die höchste Herrlichkeit und Pracht	anon	Recitative	S			Org Bc	E minor
6	Ach wie flüchtig, ach wie nichtig	Franck	Chorale	SATB	Co Ft 3Ob	2Vl Va	Org Bc	A minor

The opening chorus, "Ach wie flüchtig, ach wie nichtig" (Ah, how fleeting, ah how insignificant),[1] is a chorale fantasia. The instruments play concertante music, to which the soprano sings the cantus firmus line by line. The lower voices act as a "self-contained group", mostly in homophony, and "declaim the individual lines of text in unison at the end of each choral passage, using a melodic formula derived from the beginning of the hymn." Bach illustrates the imagery of the text, "fleetingness and insubstantiality" in motifs such as "abrupt chords separated by pauses and ... hurrying scale figures".[6] Gardiner comments:

Long before the first statement of Franck's hymn (sopranos doubled by cornetto) Bach establishes the simile of man's life to a rising mist which will soon disperse. Fleet-footed scales, crossing and recrossing, joining and dividing, create a mood of phantasmal vapour.[7]

The musicologist Julian Mincham compares the instrumental music to "mist and fog, images which imply movements of wind and air" and hears the lower voices as "evincing a feeling of primeval power and solidarity".[8]

In the first aria, the text "So schnell ein rauschend Wasser schießt" (As quickly as rushing water)[1] is illustrated in the flute, the violin and the tenor voice by "fast-flowing" music,[6] "each musician required to keep changing functions – to respond, imitate, echo or double one another – while variously contributing to the insistent onwardness of the tumbling torrent".[7]

In a recitative for alto, "Die Freude wird zur Traurigkeit" (Joy becomes sadness),[1] images such as flowers speak of transience until the grave.[8] The Bach scholar Klaus Hofmann describes it as a "far-reaching coloratura [which] culminates in an uneasy dissonance".[6]

In the last aria, an "unusual oboe trio"[3] accompanies the bass voice in "An irdische Schätze das Herze zu hängen" (To hang one's heart on earthly treasures).[1][3] Gardiner comments: "He scores this Totentanz (Dance of the dead) for three oboes and continuo supporting his bass soloist in a mock bourrée", the oboes undermining in "throbbing accompaniment ... those earthly pleasures by which men are seduced", then representing "through jagged figures ... the tongues of flame which will soon reduce them to ashes, and finally in hurtling semiquaver scales of 6/4 chords ... surging waves which will tear all worldly things apart".[7] Mincham sees a connection of the runs to those of movement 1, but points out how different their function is here:

now depicting thunder flames, stormy seas and the destruction of the world. The descending scales played in unison by the three oboes have great force. The vocalist has several prominent images, notably the long melisma on the word "zerschmettert" (shatter) and the weird, descending chromatic phrase towards the end, suggestive of a world of chaos and foolishness.[8]

A recitative for soprano, "Die höchste Herrlichkeit und Pracht" (The highest glory and magnificence),[1] expresses that even highest power will not escape death.[8]

The closing chorale, "Ach wie flüchtig, ach wie nichtig" (Ah, how fleeting, ah how insignificant),[1] is a four-part setting.[2]