This page has a vocal comparison of Paul (left) & Faul (right): http://digilander.li...ruth/audio.html
If the voice prints do not match up, then the songs were sung by different people. The studio magiCIAns at
Paul singing "Eleanor Rigby" vs. Faul:
Unfortunately, it seems that technology can mimic a person's voice making it more difficult to identify a double using voiceprints.
Please also see Paul McCartney's voice vs. Faul's voice for more information.