She lost her abbility to hear other mind-voices after an accident: still being able to project her songs, she could never be sure if they were received correctly. Knowing from others that the humans living on Sphinx were able to communicate without telepathy, she was eager to learn their ways.
She gave up her position as an elder of her clan and moved to the Bright Water Clan, because it was the one with the earliest and closest contact with humans. After years of studying them, she became the first treecat to understand the concept of spoken language, and transmitted this knowledge to others. However, she never overcame her own mental deafness.
Thanks to Singer from Silence, treecats could finally begin to understand human communication, leading to a greater understanding between the two races and the eventual development of a sign language that gave them the abbility to actually talk to each other. (HH10)