Correction:~
Having at last tracked down the CD of Lewis,there ARE two (possible) operatic pieces,one is called Songs My Mother Taught Me,and the other is Voi Che Sapete(frm the Marriage of Figaro by Mozart).
However,if you search on Amazon (under) Lewis you will find it.
Just in case the UK Amazon "sampler" player isn't working,here is a link to the German Amazon.
http://www.amazon.de/Lewis/dp/B001QH0GTQ/ref=d m_cd_album_bb
This is of course a bit academic,as you will probably want to buy the CD anyway?