The 9th String Quartet was written in Rio in 1945, and dedicated to Mindinha.
"This quartet without key signatures can loosely be designated 'atonal'." - David Nelson, from his liner notes to the Marco Polo disc including this work.
Published by Southern Music Publishers, New York.
The score and parts are available from Peermusic.
The premiere was in London in 1947.
There are two records in the Villa-Lobos Concerts database for this String Quartet as of August 2009.