Many great WW1 songs (including the two I give lyrics to above) can be found at my favorite WW1 website, FirstWorldWar.com. Their list includes song MP3s of the actual vintage recordings of these and many other songs, speeches, etc. and was just updated.

John McCormack was one of the most famous singers of this era, and recorded many of the popular songs of the era, and there are many sources of information, recordings, etc about him online.

Also, there are WAV files at Trenches on the Web here:

http://www.worldwar1.com/media.htm#clips

You can also hear samples of WW1 songs recorded from original hand cranked Victrolas can be heard here, and the tapes & sheet music ordered too!

http://www.besmark.com/ww1b.html