Luigi Labache is the most famous bass to have ever lived.

If this seems like an exaggeration, I encourage you to spend some time reading about him. Everything about Lablache was big, from his voice with its large compass, flexibility and ability to trill, to his physical size and out-sized comic genius that had audiences laughing before he opened his mouth. He sang everything—dramatic and buffo parts—to great acclaim, taught voice (to Queen Victoria no less), and fortunately for us, wrote a book about singing. You can read it here.

I first read Lablache's book at the New York Public Library, and subsequently found a hard copy at Abebooks. In terms of vocal pedagogy, it is a very desirable book. Why? Because, it contains simple and easily understandable instructions in the Italian School of Singing, from the formation of the mouth to the manner of vocalization. That may be why it was reprinted many times. 

This book is also unusual because as it is—to my knowledge—the first manual written in English to show the student how the tongue should be used during singing (the plate used by Lablache in his treatise that shows the placement of the tongue first appeared in a manual written by Crivelli twenty years earlier). Other authors of the period wrote about the tongue's placement in the mouth, but Lablache was the first to give the reader a picture. And what does it look like? Flat and grooved. My own thought is that Lablache's representation may refer to the feeling involved as well as the physical conformation.

Up until quite recently, you had to trudge to a good music library to find this book. Now it is click away. Amazing when you think about it. Instruction in the art of bel canto singing is right at your fingertips.