Audio Editing: Changing One Pitch Within A Chord

I hope there's a good solution for this!  I have a stereo recording of an a cappella SATB piece of mine.  It's excellent except for a several-second passage in which I need to change one of the pitches.  (They didn't perform it wrong -- I've since changed the pitch in the score.)

Info that might help:

- group has great intonation and blend, so all pitches in this passage are really spot on;

- the pitch in question is G above middle C and I need it to be A above middle C;

- this G is the highest pitch in the texture, sung by the sopranos;

- it's an all-homophonic passage, and two of the four parts (including the sopranos singing this G) are holding still, chanting the same pitch on several different syllables while the other parts move.

Please help me find out if there's a direct software/editing solution (as opposed to, like, "Get a different group to record it").  Thanks, I really appreciate the help!

melodyne does that.

Do you have separated recordings for voices ?

if you only have a single waveform with all voices singing at once, and you want to modify one note of the chord I don't think is possible.

It should be fairly easy if you still have the session you recorded. Track for track.
But if its all been mixed down then (as SYS65 said) I dont think its possible.

(Unless there is a program that can take apart files, I have a feeling there might be but I have never came across it when I have looked)

Wow, Melodyne does appear to do exactly that.

Downloading the demo now and will update re. whether it worked.

Thank you!

For others' reference, you may need to restart Melodyne multiple times after you do the trial authorization, to get it to work correctly.

But Holy *&^%!!  It works as promised.  (To clarify for future readers: yes, it accepts polyphonic audio as input [such as a standard stereo recording of an instrumental group, chorus, etc., performing multiple lines at once] and separates that audio into component parts so each part can be edited.)  Thank you, Kibbletime!

You're welcome.

Wow il be sure to check this out if it works as good as it sounds =D

It is pretty remarkable. 

The demo only works for 30 days, and the sw is expensive, so you may want to plan accordingly for a month when you can use it productively.