I don't know if it will interest you but if you are a PowerMac user there is:

VocalWriter 1.0 ,software synth that sings (multitimbral & polyphonic)! 
and writes 
AIFF files. Includes a GM synth. 

A 15 day trial fully functioning demo is available for download
 (4MB compressed file). $100 to register.
 Go to  

-- 
Jean-Michel DARREMONT