The "Irish tenor" is generally just a light, lyric tenor. John McCormack, or the American, Dennis Day, who was a regular on "The Jack Benny Show" way back, were good examples.

By the way, "nasality" is not good in any voice. My voice teacher, Edna Bianchi, used to say that a good singer should make good use of "nasal resonance" (or "singing in the mask" as some describe it), but without allowing the tone to get "nosey."

By way of comparison, Luciano Pavarotti could never be mistaken for an "Irish" (light, lyric) tenor. His milieu is more opera by Verdi, Puccini, and other Italian composers And certainly not Danish tenor Lauritz Melchior, who is a dramatic Wagnerian tenor. BIG voice, good for Wagnerian roles like "Siegfried" and "Lohengrin."

A good current example of a light, lyric ("Irish") tenor is Finbar Wright. Here is a clip of him singing "So Deep is the Night," a set of words written to the music of Fredrick Chopin's piano Étude Op. 10, No. 3.

HERE.

By the way, it's Finbar Wright's masterful breath control and control of nasal resonance that allows him to fill a large auditorium or theater with his voice, despite singing over an orchestra.

(I think he's about the best "Irish" tenor afloat these days!)

Don