Opera d’Oro has wonderful recordings of early singers that are collected by theme. I purchased this album in 2005 and I frequently play it as fuel for my ears when teaching.
Disc 1 is entirely female singers, and Disc 2 is male singers. It’s a worthwhile listen for phrasing, vocal color, and musicality. I would direct the listener to be aware of the vowels, clarity of coloratura passages, and the general brightness of these voices. There’s very little ‘heavy’ singing in these artists, and their work demonstrates a joyous and fully vibrant vocalism.