Thank you GUEST,Red Notes Socialist Choir, I have put you in the performers list above.

Strictly speaking Bandiera Rossa (avanti popolo), is not a Spanish Civil War song because it predates the SCW and is not about the SCW. However,it is strongly associated with the SCW because it was sung as a marching song by the Garibaldi Brigade of Italian volunteers and it was one of the songs printed in The International Brigades Songbook, Canciones de las Brigadas Internacionales.
Here is a link to the Wikipedia entry http://en.wikipedia.org/wiki/Bandiera_Rossa

There is also a Mudcat thread about the song with lots of interesting links HERE