Here is a heavy ambient verb with a vocal like quality to the attack. It uses the formant filter into a multidelay then reverb. Use different vowel sounds to change the vocal quality. Watch for resonant peaks when resonance is high. for this example I have Resonance extremely high, I compensate by notching the reverb to keep some of the ringing down.
http://javajunkiemusic.com/Audio/Java_Vocal_Verb 11.syx
http://javajunkiemusic.com/Audio/Java_Vocal_Verb 11.syx