In 1951 Villa-Lobos wrote one of his very strong late-period orchestral works, a ballet score written for La Scala called Ruda, subtitled The God of Love. There's only one recording of this work that I know of, the 1996 Marco Polo disc that includes Ruda and the Sixth Symphony, played by the Slovak Radio Symphony Orchestra, conducted by Roberto Duarte.
In the last few days I've really been enjoying reading Villa-Lobos reviews in the brand-new Gramophone Archive. The reviews written by Lionel Salter from the 1950s through to the late 1990s are especially insightful. Reading a bunch of these reviews in a row is like a critical master class in the music of Villa-Lobos; Salter really knows his stuff. That's especially impressive when you consider the lack of context Salter had available in the earlier years: today's reference works, recordings, and scores weren't available at the time. Salter would have been lucky to have heard three of the symphonies in the late 1990s; we can now easily listen to all of the surviving works, and a few in multiple recordings.
As it happens, L.S.'s review of the Marco Polo disc is quite negative regarding the Sixth Symphony. But he absolutely loves Ruda. The "God of Love" theme, according to Salter,
"... was right up Villa-Lobos's street, affording him boundless opportunities for compulsive rhythms, misterioso passages, lushly lyric episodes (there is one in the Inca movement and another, somewhat Ravelian, for the Mayas), exotic melodic lines and, in places, wonderfully original instrumentation."
At this point in the review Salter has an interesting aside: "I believe the score includes a part for the Sonovox, but I was unable to detect it in the general melee."
Villa-Lobos's interest in out-of-the-way and especially in new technology instruments is well known. I've written about Villa's early use of the prepared piano, and, in Amazonas (1917), the use of the violinophone and the sarrusophone. The score for Ruda (the autograph of which is in the Museu Villa-Lobos) includes a part for the "solovox".
What is the solovox? Might it be the Hammond Solovox which according to this site was manufactured starting in 1940? This early electronic instrument is shown in this picture: "The Hammond Solovox consisted of a keyboard and a "tone cabinet" (speaker/amplifier/tone generator)."
Or is Villa-Lobos writing for a Sonovox, an electrified "talk box" which amplified the sounds made from a pickup placed right on the throat. Think about the sounds from 1940s Disney films: the "All Aboard! Let's Go!" sound in the Casey Jr. segment from Dumbo, and the interesting sounds in The Reluctant Dragon (both from 1941).
This is an interesting possibility, since at the time Villa-Lobos was hanging out with Disney's animators who were in Brazil working on their Good Neighbor masterpieces Saludos Amigos (1942) and The Three Caballeros (1944). At the same time, Walt himself was considering the Little Train of the Caipira movement of Bachianas Brasileiras as a scene in 1940's Fantasia - a fascinating might-have-been. Is Villa-Lobos picking up new techology tips from Hollywood?
A peek at the Ruda score would help; I'll listen very carefully to Ruda with headphones to see if I can hear anything myself. Go to this page on Ruda for more about this interesting work.