After the French premiere of Amériques in 1929, where the composer replaced the siren with an ondes Martenot, he decided to move electronic instruments to the foreground in upcoming compositions.
For the 1961 revised version, the composer would choose the ondes Martenot, which had become much more popular in France in the 40s and was generally easier for play for keyboard players.
"[6] The text used for the bass or male chorus is translated into Spanish by Francisco Ximénez from the original Mayan Kʼicheʼ book Popol Vuh.
[3][7] The composer chose to include the text in its original Spanish, as he had a good command of the language and preferred its authenticity over the French translation.
For this reason, Varèse specifies that a typical performance "should be dramatic and incantatory, guided by the imploring fervor of the text, and should follow the dynamic indications of the score.
[9] Ecuatorial received mixed to positive reviews by critics, who were surprised by Varèse's style and generally noted the used of the theremin in concert performances, which was a novel rarity at the time.
The New York Herald Tribune also described the "piercingly shrieking theremin instruments" and stated that "the plan and purpose of the outlines of the music and Mr. Varèse's scoring ... was not always clear, but there were many pungent, massively expressive measures.