General impression
The first song of the Lieder ohne Worte Op. 19 by Mendelssohn honours its name: a very singable melody (cantabile...) with a flowing chordal accompaniment consisting of not too complex harmonies.
Surprising alterations here and there cause an effect which draws the attention of the attentive listener. The bass line moves “like a melody” in a, for the greater part, stepwise motion; first in contrary motion with the melody, later, in the contrasting middle section also in parallel thirds and ascending which creates a increase of tension. In this way the bass line disconnects itself from a strictly harmonic role, creating a two-part play with the melody.
Form
Globally we have a form we could lable as A :|| B – A . Or:
A – A – B – A. We can call this a Barform (German: Stollen – Stollen – Abgesang) followed by repeat of A. The transition to B is marked by a sudden colour change by the introduction of an e-minor chord.
Melody
The melody is not just good singable, but also balanced in proportions by grouping measures.
A B A
4+4+5 4+...4+2+1+1 4+4+8
When expectations are not fulfilled and a continuation is different than expected, that is the effect of “feints” or “diversions”, after which a satisfactory conclusion folllows. This goes for the (“sudden”) a in measure 13 and the d in measure 43 for example.
Several times the composer plays with the expectation of the listener, for example by introducing alerations (the a in measure 13 and the d in measure 43) or a surprising alterated chord with a special colour effect; a colour effect achieved by the change from the G major chord to a B major chord (25-27): this a typical example of a mediant relation which plays in romantic music an important role as a means of expression.
Beginning
We hear two introductory measures consisting of two harmonies, I and V, composed out by a bass-line consisting of (1) – (3) – (2) – (5), after which the tonal playing field has been indicated: E major is the main or primary key.
E – B - :|| e – G – (concluding with the Upper Mediant B) – E .
A first phrase ends on the dominent of E (V) after which in the consequent the predictable conclusion is not (immediately) chosen (by resolving the a# as a leading tone to b), but by making it descend to a-natural (being part of a diminished seventh chord) followed by an extension which gives the conclusion already expected (I inB major) which functions as a dominant of the repeat.
In the beginning we hear a movement from E major to the dominant key of B major; a minor seventh is added after the repeat. In that way a bridge is created to the e- minor chord (17), which gives a clear change of mood, marking the beginning of the contrasting central section.
The middle: contrasting section
In the contrasting section the mostly descending movement of the A part is replaced by an ascending melodic motion. This effect is being reinforced by the moving of the bass-line in parallel thirds with the melody. This results in a building up of tension, for which there exists a nice German term: “Steigerung”.
The suggestion of e minor proves to be temporary; quickly there is a move to the use of the tones of the G-major scale, after which a short quasi cadenza fragment follows. The confirmation of G major as the new tonic is not followed through: the note b in the melody becomes part of a so called “phrygian cadence” (IV6-V). The b functions not as a third of a G major triad, but as the root of a B major triad.
The melody note b is being played around (b-c-b-a#-b) in measures 25-29 after which the B major chord resolves to the tonic of the main key E major and the A part reappears in a slightly modified form.
Harmonically the main key is not left again; everything comes to rest. A rest which is enhanced by the use of a pedal point on the tonic during the last 6 measures.