Complex sentence: It was designed to be sung in the large bedrooms where the nobility often entertained their intimate friends, and were usually improvised songs on the themes of gallantry and love, in the form of a dialogue, performed with the lute and the théorbe.
Split into simpler sentences: It was designed to be sung in a large room (chamber) where the nobility entertained their intimate friends. They usually were improvised songs on the themes of gallantry and love, in the form of a dialogue, performed with the lute and the théorbe.