Counter-melody

The accompanying texture, too, is rather more than a simple filling in of the harmony. In the first phrase, for example, the beginning of the counter-melody in the Sextus part is shadowed in shorter note values in the tenor of Choir 1 and the alto of Choir 2, while the rising scale of the plainsong (bars 2-3 (Bt 3-5)) is shadowed by the bass of Choir 2.

Source: wiktionary

This section has compositional elements including melody, counter-melody, sustained harmony, rhythmic harmonic accompaniment, bass line and rhythmic accompaniment, but they are all marked mf.

Source: wiktionary

The first violin played the tune throughout, the second violin and the viola played after-beats (the pahs), the cello had some kind of sustained counter-melody or doubled the bass, who played the ooms.

Source: wiktionary