Three ways of buying singing material on the web or of listening to your part free:

1. To buy a score or a recording just of your part (£10 for a cd or £8.50 for a casette), or a recording of a performance, go to
http://www.musicdynamics.co.uk/store/buycline.aspx

2. To buy a recording just of your part (£8 for a cd) go to
www.cyberbass.com

3. To hear for free a piano version of your part, go to
www.cyberbass.com
and click on "Index" half-way down the page in the middle,
select the composer and work, and click on the movement.