Mária Basilides completed her studies at the Music Academy, initially in singing and then in opera, as József Sík's pupil. Following her graduation concert, a critic praised her "beautiful ringing mezzo-soprano tending towards the alto". She made her debut in the Népopera (Folk Opera), which was set up at that time to put on pieces that were never performed in the Opera House, or neglected works. She sang the role of Poppea in the opening performance of the theatre, in Nouguár's opera, Quo Vadis. Later – in order to survive – the Népopera also put on pieces which were in the Opera House's repertoire, and thus, by 1915, during Basilides' time at the theatre, she had sung Azuena, Mignon, Carmen and Ulrica. In 1915 she was given a contract by the Opera House, and was from then on one of the Opera's shining stars right to her death.
It took István Kerner's ears and, no less, his eyes to discover her potential waiting to be brought to the surface. He first entrusted her with the title role of Gluck's Orpheus, and he allowed her to perfect her performance step by step. Gluck's music could have been at the same time preparation for the great Wagner roles to come. Two decades after the 1917 Orpheus, however, she played in another Gluck opera, in the Iphigenia in Aulis. As Queen Klytemnestra she dazzled the audience with her royal bearing, magnificent rage, and movingly human voice.
In the meantime, thanks to István Kerner, who also gave concerts as the chairman-conductor of the Philharmonic Society Orchestra, Mária Basilides also participated in the performance of Beethoven's Ninth Symphony, and this was followed by other works, the Missa Solemnis and songs by the German master.
It was also Kerner's decision to revive the cult of Wagner, which, however, required all the fist-class voices in the Opera House. Basilides took on one after the other of the alt roles of these music dramas, and in the course of the years became more and more at home in their atmosphere. She endowed the roles of Fricka and Erda in particular with many of her own ideas and individual colours.
It was on 10 March 1921 that Mária Basilides performed the role of Delilah in the Opera House for the first time. This role was, and thereafter remained, one of the masterpieces of her constantly improving acting talent.
Her repertoire was extremely wide: she was an excellent Marfa, Gertrudis in Bánk Bán, and Countess in the Queen of Spades. She was the first Hungarian Marfa in Khovanschchina, she sang the Housewife in the Trasylvanian spinning room. She often appeared as a guest artist abroad; in the twenties she was a constant guest in Berlin. The highest peaks of her operatic career were those roles which required Basilides's supreme knowledge of styles and musicality: The messenger in Monteverdi's L'Orfeo and the two Erdas. These roles were closest to her noble personality. She was not one of those singers who use spectacular means to achieve powerful effects: she never used her beautiful, well balanced and at the height of her powers velvety soft voice purely for itself.
She attained Europe-wide successes not only on the opera stage; she was an even greater master of singing oratorios and songs. After the successful Ninth Symphony, there was practically no oratorio performed in Hungary without Mária Basilides singing the alt solo. The next step was the Mozart Requiem, and then – encouraged by its success – came at Christmas Handel's Messiah and at Easter Bach's Saint Matthew's Passion. Later the Bach repertoire further expanded with the H minor Mass and several, memorably performed, cantatas.
She was an inspired and authentic interpreter of Mahler's vocal compositions; for decades
it was her concerts of songs that kept the cult alive. "It is not the popular Schubert that she brings to us; she has exhibited the shattering depths of Shubert's dark nearness to death" – wrote Aladár Tóth, whereas a German critic asked: "Who else sings Schubert songs like her?" She was one of the most important propagators of Hungarian works, mainly the creations of Bartók and Kodály. She was a permanent member of the Opera House.