1929 - 1933 Grammar school in Martin
1933 - 1937 College of education in Spišská Kapitula (singing, piano and violin)
1937 - 1939 teacher in Smolenice
1939 - 1942 teacher in Bratislava
od / since 1939 Private study of singing at Anna Korínska
1939 - 1942 soloist of the Opera ensemble of the Slovak National Theatre in Bratislava
1942 Scholar at Riccardo Stracciari in Rome
1943 - 1944 scholarship student with profesor Balzarová in Vienna, at the same time he acts in Volksoper in Vienna
1944 - 1946 soloist in Opera in Slovak National Theatre in Bratislava
1946 - 1947 soloist in Prague Opera
1947 - 1948 soloist in Opera in Slovak National Theatre in Bratislava
1948 - 1967 soloist in New York City Opera Company in the USA
Rudolf Petrák began his career as soloist in the Singing Choir of Slovak Teachers, later he was starting soloist in the Opera ensemble of the Slovak National Theatre. He played there minor roles from opera and operetta repertoire. His artistic progress was supported by exchange scholarships, as well as by his acting in Rome and Vienna, and then he returned to the Opera ensemble of SNT as an excellent performer of lyric tenor roles. He portrayed the following roles in the Opera ensemble in that period: Lyonel (Marta), Janík (The Bartered Bride), Rodolfo (La Bohéme), Duke (Rigoletto), Tsar Berendey (The Snow Maiden), Count Almaviva ( The Barber of Seville), Manrico (The Troubadour), Alfredo (La traviata).
Rudolf Petrák often performed in radio broadcasting, interpreted the Slovak folk songs with piano accompaniment of Rudolf Macudzinský and also songs of M. Schneider-Trnavský, V. Figuš-Bystrý, R. Schumann and others. He regularly had concert activities (up to his departure to USA in 1948)on the concert stage of the Reduta Bratislava, Government building and many Slovak cities. The activities included occasional solemn concerts, many benefit concerts during war and they contained songs and opera repertoire in which Mária Kišonová-Hubová and Margira Česányiová often participated.
In 1948 Rudolf Petrák left for the USA where as a soloist in New York City Opera Company acted until 1967. With the opera company he went on tours in American cities and he often acted in Philadelphia with companies Scala Opera Company, Pittsburgh Opera Company or as a soloist in Pittsburgh, New Orleans, Canada, Mexico and Virgin Islands. He cooperated with a lot of eminent singers like Eleanor Steber, Nell Rankin, Dorothy Kirsten, Jarmila Novotná, Leontyne Price, Herva Nelli, Martha Lipton, Regina Resnik, Roberta Peters... and conductors like Arturo Toscanini, Erich Leinsdorf, Leopold Stokowski, Eugéne Ormandy, Thor Johnson, Tullio Serafin, Jean Morel, Joseph Krips, Igor Markewich...From the beginning of his opera career in New York he devoted to concert activities and collaborated with a big number of orchestra ensembles (f.e. Baltimore – Symphony, Rochester Philharmonic), he sang tenor parts in a lot of vocal – instrumental works. In his concert repertoire there were songs from Slovak composers like M. S.- Trnavský, Eugen Suchoň, Alexander Moyzes, Dezider Kardoš, Tibor Freš and mainly Slovak folk songs which he recorded in private publishing house Marina Records. He often performed in American radio and TV programmes. He recorded a lot of gramophone records from classical music, operas and arias for a lot of recording companies (Telefunken, Columbia, Everest,MGM and others).
The Conservatory of Žilina has been organising a vocal competition with the name of Rudolf Petrák since 2008.