In Ravel's "Bolero" the violas play a repeated pattern in pizzicato that grows more and more complex. The second form, however, beginning at m. 21, has a notation that puzzles me. The middle notes show the same note being played at the same time with the same length. Like so:
The notation implies one voice only and the length shows it's not a note that carries over the next, which would be more or less meaningless for pizzicato anyway. I cannot seem to find anything about it when searching online. My best guess is that the same two notes should be played on different strings to achieve a double layer of that note, but it's only a guess and I'd like to know for sure.
While I have not read many orchestral scores I've read quit a lot of notes and it's the first time I've come across it. My searches have given me info on notes of different lengths for the piano, notation of same notes for different voices for vocals, but nothing that explains this.