I would like to purchase The Penguin Book of Early Music.  There are
perhaps two editions (different volumes?), one edited by Rooley,
another by Witmark.  I am specifically looking for vocal music.  Can
anyone tell me where I can order these?

Hi Celebrian,

Thanks for the question. The Penguin Book of Early Music edited by
Anthony Rooley is currently out of print but you can purchase a used
copy at:

Abebooks.com
http://dogbert.abebooks.com/abe/BookDetails?bi=203899647

The Library of Congress entry for this book makes clear that it deals
with vocal music.  The full Library of Congress record can be found
at:
http://catalog.loc.gov/cgi-bin/Pwebrecon.cgi?v3=1&ti=1,1&SEQ=20031012104007&Search_Arg=penguin+book+of+early+music&Search_Code=TALL&PID=15657&CNT=25&SID=1

I found no record of a Penguin Book of Early Music edited by Witmark. 
I searched the Library of Congress Online Catalog and only found the
Rooley edition.  There are however a number of music related books
that were written/edited by members of the Witmark family.  A listing
of used copies of these books may be found at:
Bookfinder.com
http://www.bookfinder.com/search/?author=witmark&title=&submit=Begin+Search&new_used=*&currency=USD&mode=basic&st=sr&ac=qr

I'm quite sure that there is no Witmark edited version of the Penguin
Book of Early Music. If you think that the Witmark book might be under
a different title and does not appear in the bookfinder.com list I
provide above, please request clarification and I would be more than
happy to try and track it down.

Search Strategy:

bookfinder.com
http://www.bookfinder.com/

Library of Congress
http://catalog.loc.gov/webvoy.htm

Abebooks.com
http://dogbert.abebooks.com/

alibris.com
http://www.alibris.com/home.cfm

If you are unsatisfied with any portion of this answer please do not
hesitate to request clarification.

Best of luck!
-Blinkwilliams-ga

Thank you for a great speedy answer!  I found the book and ordered it
immediately for my daughter for Christmas.