Didn't see this mentioned, and quartet no.3 may be the only one of his quartets to be at all known by anyone at all (because there's another commercial recording, and - another?? - recording that airs on Euroclassic Notturno from time to time), but volume 3 of cpo's set of the complete works for string quartet by Henri Marteau, with his 3rd string quartet in C major (Op.17) and 8 lieder (op.10) for soprano and string quartet, is expected (https://www.prestomusic.com/classical/products/9371703--henri-marteau-complete-works-for-string-quartet-vol-3) out 7 October.
Presto, who may be quoting cpo's notes, or ... writes of the op.10:
"The CD is supplemented with the "Eight Songs with String Quartet Accompaniment," op. 10 speak, written in 1905. In these songs Marteau is far ahead of his time, because it is the first string quartet of its kind in which the human voice also has its say."
Given that there's at least one, probably several, work(s) called "string quartet" from the 19th century which have vocal parts, and innumerable works that are lieder with string quartet accompaniment, I'm not sure what to say to this.
We can judge for ourselves here:
https://www.jpc.de/jpcng/cpo/detail/-/art/henri-marteau-streichquartette-vol-3/hnum/6100148
I should edit "innumerable" to ... at least a few (at least judging from early enough works on imslp ;))
Ah I see, Presto's notes are just a translation of cpo's.