Opus is not descended from Vorbis. It's descended from CELT and SILK. CELT was developed by Xiph.org, SILK by Skype. The CELT portion handles complex, arbitrary

Opus is not descended from Vorbis. It's descended from CELT and SILK. CELT was developed by Xiph.org, SILK by Skype. The CELT portion handles complex, arbitrary audio like music and sound effects. The SILK part handles voice. Xiph, Skype, and IETF (among others IIRC) pooled their expertise in CELT, SILK, and the standards track respectively. Xiph.org did develop Vorbis though.