Stretching audio without distortion or break up

Help!
 
So Ive been experiencing with stretching audio waves. What I notice is that when I stretch a wave it seems to distort or break up the more/longer I stretch it.
 
For example:
I have this audio of a girls voice. She sings a extended note and holds it. Im using that audio clip as apart of a song I'm creating but, the note she is holding doesn't really hold out as long as I need it to in order for it to fit with the part in the song.
So, I take the clip and stretch it. However, I notice when I do that it breaks up and creates artifacts and distortion. Its not as clean and creates a effect I don't want.
 
So, I ask. Is there a way to stretch the clip without the artifacts and distortion? Is there a way to stretch the clip and have it be clean and smooth?
 
I'm trying to wrap my head around this. I wonder if it can even be done.
 
Thanks again for all the help.

If you're not recording and processing at 64bit float...you will find this is your problem. It fixes about 90% to 95% of these types of granular processing distortions...depending on how far you stretch said audio, and indeed depending on the codec.

Thanks again guys