In this piece choir one is labelled proposta and choir two risposta.
This Canzon in ecco, comes from Grillo’s Sacri Concentus ac Symphoniae, published in Venice in 1618.
Dynamics are not marked in the parts, except for the continuo part, which is marked “ecco” whenever the risposta choir is playing (the dotted lines in the edition indicating the duration of the ecco are, of course, editorial).