Son of a painter who used to sing operas in his free time, Gastão Formenti successfully developed talents in both areas. In the popular music, Formenti had great success as a romantic singer, also recording several themes in the then-fashionable styles sertanejo (folk) and folkloric (with highlights for his renditions for Waldemar Henrique's tunes in 1934 and 1935), along with a few Carnival hits. One of the great Brazilian singers, Formenti recorded more than 300 compositions. Formenti was also awarded as painter, at Portugal's Eight Centennial and the Brazilian Salon of Fine Arts. His paintings are exhibited in the Museu Nacional de Belas Artes, Museu de São Paulo, and in museums in the United States and France.
In 1927, Formenti opened in the Rádio Sociedade with success and was immediately hired. In the same year, he recorded his first album, through Odeon, with the anonymous sertanejo song "Anoitecer" and the tango sertanejo "Caboclo Apaixonado" (Marcelo Tupinambá). The first hit came in 1928, "Casa de Caboclo" (Hekel Tavares/Luís Peixoto, based in motifs by Chiquinha Gonzaga). In 1929, he also had success with the valse "Hula" (Joubert de Carvalho/Olegário Mariano) and the song "História de Toda Gente" (Joubert de Carvalho). Moving to Rádio Mayrink Veiga in 1930, he was (together with Carmen Miranda), one of the first two artists to sign a contract in radio. He had success with "Glória" and "Brincando Com Foguetão" (through Columbia, 1931), the cateretê "De Papo Pro Á" and the song "Zíngaro" (both by Joubert de Carvalho/Olegário Mariano), and the fox "Beduíno" (Joubert de Carvalho/Olegário Mariano) and the valse "Se Ela Perguntar" (Sivan Castelo Neto). His biggest hit was the all-time classic (since its release by him) "Maringá" (Joubert de Carvalho), recorded in 1932. He also had success with "Na Serra da Mantiqueira" (Ary Kerner), recorded in 1932; the valse "Folhas Ao Vento" (Milton Amaral), recorded in 1934; "Samba da Saudade" (Ronaldo Lupo/Saint-Clair Sena) and "Coração, Por Que Soluças?" (José Maria de Abreu/Saint-Clair Sena), recorded in 1937, the year in which he left Victor for Odeon, where he would stay until 1939; and the valse "Não Sei Pra Que Viver" (Saint-Clair Sena), 1939 (already through Columbia). In 1942, he retired from the artistic scene with the advent of the auditorium shows. But he still recorded other albums (in 1947, 1952, 1956, and 1959).