all is possible: open csf file in winhex or other and copy part from hex - 08 08 08 to next part with 08 08 08.(its voice in digital) Safe this part like .vox . Open with Sound Edit or other like vox 16000, modify this file only voice part- must be same size and same start part(08 08) of and end(08 08). Safe. open this modify file and return to the original place in csf file. Its work, I have try it.