The "lighter forms" refers to Einstein's categorization of 17c lighter secular music--frottole early on, followed by later villanellas, canzonettas, etc. I'll separate things out by composer.
Madrigals:Lighter
More to come: Alessandro Romano, Adriano Banchieri, Baldassara Donato, Benedetto Pallavicino, Bernardo Giacomini, Claudio Merulo, Giacomo Gastoldi, Giovanni Battista Conforti, Giovanni Croce, Giovanni Ferretti, Giralmo Conversi, Giuseppe Caimo, Jean de Castro, Jhan Gero, Luzzascho Luzzaschi, Marc Antonio Ingegnieri, Mateo Flecha, Orazio Vecchi, Orlando di Lasso, Perissone Cambio, Palestrina, Philippe Verdelot, Stefano Rossetti, Vincenzo Ruffo, and others.
The big collections are above, though.