He carried out a great number of performances, over 650 in the 36 operas represented at New York's Metropolitan Opera alone, where he was able to renew his contract for over thirty consecutive years (a record never equalled). He is friend and admirer of the great Caruso who during his first performances of Canio in I Pagliacci by Martinelli, as a gift gives his costume to the young tenor in sign of respect and friendship. The most challenging operas which were sung by the great tenor before his death were assigned to Martinelli, the only one able to emulate him. He then sings "La Juive" and "Otello" of which he becomes the most famous performer. After becoming a real star during the "roaring years" of America, he establishes relationships with outstanding personalities which marked the history of those times especially in the United States where he is still celebrated and loved today.
When in 1967 at the age of eighty one, almost just for fun, he accepts to perform the Imperatore from Puccini's Turandot, replacing the second lead, he astounded the audience and critics for his ability to hold his breath, his confidential high pitch and the renowned scenic appearance.
Finally in 1968 Martinelli records "Perché volete voi" Zandonai's Francesca da Rimini, a symbolic last will and testament of the artist's voice who dies a year later in New York on 2nd February 1969.