It´s been exciting to read the news and reviews about the Met´s new Tosca production since the Leading Lady, Tosca herself, Karita Mattila went to the Sibelius Academy together with me. Yet another success for her! (let´s not mention the director). Karita and I started the same year as voice majors – and look where she is now! Of course, her voice was exceptional even then and if I recall, she was only 19. And her energy – it would just burst out with her eyes shining in that marvelous face with wide cheekbones. I remember she was taught to sing in(to) the masque  by her teacher Professor Liisa Linko-Malmio. ( I´m not to guess what Ms. Mattila thinks about voice production today.) But what masque, someone may ask?
So, that brings us to this question: Can a Voice be Placed? Of course not,  voice scientists argue, you cannot PUT the voice anywhere. It will resonate in all the cavities anyway, given that there is a good balance of airflow and vocal fold closure. Yet, why do some teachers still talk about placement in the masque, advocate it, even demand it from their students? Why do many singers feel the sympathetic resonance in the front of the face, around the eyes and nose? YES, I say, the feeling of the masque is real and it can be a very good tool for fine tuning the optimal sound. Because that´s what it is: trying to mold the vocal tract so as to gain maximum resonance and carrying power (over the orchestra without amplification). The sound will then be chiaroscuro (that great Italian word for both bright and dark), combining high resonance brilliance with slightly lowered larynx and deep body connection.
All this applies to classical singing. It is an ART – and as such perhaps not the most natural thing in the world (excuse my sarcasm, tongue-in-cheek!). I usually don´t  teach this concept to a beginning singer. But when coaching all those wannabe opera singers it is of paramount importance that their utmost potential, their own optimum and maximum resonance quality be found. It will enable them to get more volume and roundness and, done correctly, also ease. No need to push or strain – just let the voice bloom with a vertical forward feeling, almost as if it were outside of yourself (remember, it´s just a feeling). So many things in singing are really not physically or anatomically equal to the sensation they cause. That´s really strange but true. And also the reason why we may get mixed up by cause and effect. To deal with that is the art and craft of a singing teacher.
Remains the answer to the question: HOW is it done?
Just a few ideas:
Experiment with gravity: lean your head over and LET your  sound flow in the cavities around the nose. (I´m well aware that the sinuses don´t actually resonate, thanks to late William Vennard).
Get the feeling of air circling in the nose, imagine smelling something. Take a “devious sneer” (thanks to Paul Farrington for that!).
Lift your upper lip with your finger while singing /U/ (funny, but it works; thanks to David Jones!).
Don´t be too stingy with your airflow – “let the airflow do the work!” (Oren Brown). Of course, the vocal folds must accomodate this airflow, vibrate it to sound wihout breathiness.
Experiment!