I have found the following books, manuals and listening to be a ‘pathway’ to studying a way of singing that some refer to as ‘Bel Canto’. Others may refer to it as the ‘Old Italian School of Singing’. Others may describe it as the ‘Italian School of Singing’. (For me, the last description is unreliable because the Italians adapted their singing techniques in the early 20th century to meet the new demands placed on the voice by verismo composers).
There is a great deal of confusion about the term ‘Bel Canto’. This is because the term can mean different things in different contexts. The list below is the ‘pathway’ to ‘Bel Canto’ as I understand it to be; a way of singing as described by Celletti (see below) and taught by Klein’s phono-vocal method (see below) and heard on some (not all) of the early gramophone recordings (thankfully there are some modern examples of ‘Bel Canto’ too, see below).
I don’t think ‘Bel Canto’ should be only academic. I think it must be experienced in the same way that riding a bike must be experienced. In other words, studying books on how to ride a bike does very little for the person who cannot ride a bike but wants to go for a bike ride in Amsterdam. Accordingly, I recommend a good starting point is to try the exercises of Garcia Snr. or Melba (see below). Both books are uncomplicated and free to download on the internet.
Celletti, Rodolfo. A history of Bel Canto. Oxford University Press. 1991.
Garcia, Manuel,Snr. Exercises pour la voix. Between 1819-1822?
Garcia, Manuel, Jnr. Hints on Singing. Canoga Park, Calif. Summit Pub. Co. 1970.
Klein, Hermann, and William R. Moran. Herman Klein and the Gramophone : Being a Series of Essays on the Bel Canto (1923), the Gramophone and the Singer (1924-1934), and Reviews of New Classical Vocal Recordings (1925-1934), and Other Writings from the Gramophone. Portland, Or.: Amadeus Press. 1990.
Melba, Nellie Dame. Melba Method: Part One. Breathing and Other Exercises, Examples, and My Daily Exercises. Part Two. Vocalises. London. Chappell & Co. 1926.
Nicola Porpora. 25 Vocalizzi. Published somewhere between 1686 and 1768.
Pilotti, Katarina. On my re-training to Chiaroscuro. Master’s Thesis at the Academy of Music, Orebro University, Sweden 2009.
Radomski, James. Manuel García (1775-1832): Chronicle of the Life of a bel canto Tenor at the Dawn of Romanticism. Oxford University Press. 2000.
Daniel James Shigo, and Hermann Klein. Hidden in Plain Sight : The Hermann Klein Phono-Vocal Method Based Upon the Famous School of Manuel Garcia. New York, NY: VoiceTalkPublications. 2013.
Striny, Denes. Head First: The Language of the Head Voice: A Concise Study of Learning to Sing in the Head Voice. 2007.