Januário de Oliveira was one of the main Columbia artists, having recorded almost his entire discography with that company: of his total of 113 songs (from 1929 to 1938), 80 were recorded at Columbia. Oliveira debuted at Rádio Sociedade and switched to Rádio Clube do Brasil, having been taken by Sinhô in 1929 to São Paulo, where he developed his entire career. In the same year, he recorded two songs at Columbia by Sinhô (who also participated in the recording at the piano): "Chequerê" and "Nossa Senhora do Brasil" (a tribute to the Brazilian modernist painter Tarsila do Amaral). In that city, Oliveira was hired by the Rádio Educadora Paulista, then by Rádio Record (where he got from César Ladeira the nickname of "A Voz de Veludo," or "The Velvety Voice") and Rádio Difusora; the latter in 1935 on the program Programa da Saudade, the most popular of São Paulo's radio.
In 1930, Oliveira recorded "Dança de Caboclo" (Heckel Tavares), accompanied by the author, and in the same year he had a hit with the Carnaval marcha "Quebra, Quebra Gabiroba" (Plínio Brito). Four years later, already hired by RCA Victor, he recorded the valse "Meu Destino" (José Maria de Abreu/Carlos Rego Barros de Sousa), which was launched in the next year with success. In 1935, he had the main role and also sang in the film Fazendo Fita (Vitório Capelaro); participating in the inauguration of the Rádio Farroupilha de Porto Alegre (Rio Grande do Sul), he performed in duo with Carmen Miranda the samba "No Tabuleiro da Baiana" (Ary Barroso). In 1936, in a duet with Arnaldo Pescuma, he had success with "Mulatinha da Caserna" (Martinez Grau/Ariovaldo Pires; which was awarded the first-place prize in the marcha category in the Carnaval contest promoted by the Mayoralty of São Paulo) and "Paulistinha Querida" (Ary Barroso). In the same year, he toured southern Brazil with the Italian singer Carlo Buti, remaining for two years in Porto Alegre (Rio Grande do Sul), having been hired by Rádio Farroupilha.
In 1938, having returned to São Paulo, he began his career as a humorist, performing during the '40s on the Rádio Nacional, casinos, and clubs around the country with his peculiar and skillful imitation of the four tessituras (baritone, tenor, contralto, and soprano). Becoming an impresario in 1949, he abandoned his career as a performer.