I thought those 64-chord ringers were enough, but NEC didn't. They went ahead and developed a 128-chord chip with support for 3D surround sound (as is included in the FOMA 901i series).

NEC Electronics has announced the 128-chord "μPD9971" PCM sound source chip for mobile phones o­n March 29th. Sample shipments have begun, and the chip is scheduled to go into production in August.

This sound source chip uses a core from FueTrek that can use a "3D Positioning Function," for virtual sound sourcing. It supports the "3D Surround" DoJa API introduced with the DoCoMo 901i series, and NEC Electronics has said "it can produce 3D surround sound for games intended for the 901i series."

128 chords is the highest chord count in the industry. The chip also includes 7 types of audio effects such as "reverb" for echoing sounds and "chorus" for making a single sound sound like many.

Inspired by:
http://www.itmedia.co.jp/mobile/articles/0503/29/news047.html

Press Release:
http://www.necel.com/mobile/melody/ja/product/pd9971.html