he composed music for works by Alejandro Sieveking and Isidora Aguirre, including Asunto sofisticado and La dama del canasto, respectively.
Later, he would ask her to compose the soundtrack for his only play, Fulgor y muerte de Joaquín Murieta, premiered in 1967 at the Antonio Varas Theater, under the direction of Pedro Orthous.
The work, which made a successful tour of Europe, tells the story of Joaquín Murieta, a Chilean gold prospector who comes to California in search of fortune.
On December 14, 1998, the two-act opera Fulgor y muerte de Joaquín Murieta, composed by him and with a libretto based on the homonymous work by Neruda, premiered at the Municipal Theatre of Santiago.
[3] In 1967, he worked with the singer-songwriter Víctor Jara in the musical arrangements of some of the songs on his self-titled album, at the same time he directed his orchestra that he accompanied on the tracks "El aparecido", "Solo" and "Así como hoy matan negros".
[2] He together with the singer-songwriter Victor Jara and the lyricist Claudio Iturra, he composed "Venceremos" the electoral theme of the socialist president Salvador Allende and a world anthem of leftist movements.
[4] About three months before the 1973 Chilean coup d'état against La Moneda, he recorded "El pueblo unido jamás será vencido" together with the group Quilapayún, a recognized worldwide protest anthem.
[4] Ortega worked with his eldest son, Chañaral Ortega-Miranda (later member of the French faction of Quilapayún), on an operatic version of Pedro Páramo, the novel by Mexican writer Juan Rulfo.