I believe it was sung a capella & the group had at least 4-5 members.

Hello Dlsinclair, 
        
Thank you for your question.


According to Roger Clarke’s Musical Performances of Waltzing Matilda
Website, it was Tina Arena who sang Waltzing Matilda at the Australian
Open in 1994.
The following excerpt from his webpage: 

“Tina Arena. She sang it at the Australian Open Tennis Championships
in 1994 and the Australian Football League (AFL) Grand Final in 1995
(but there don't appear to be any recordings of her singing it). Yes,
that's the same Tina Arena who sang at the Opening Ceremony of the
Sydney Games in September 2000.”

Roger Clarke’s Musical Performances of Waltzing Matilda Website
http://www.anu.edu.au/people/Roger.Clarke/WM/Perf.html

I double checked this information in a search for Tina Arena.
On the Tina Arena Website it says:

“This coincides with Tina’s performance at the Men’s Final of the
Australian Open, where she performs ‘Waltzing Matilda’ to a worldwide
audience of 70 million people.”

Tina Arena Website
http://tinaarenaonline.free.fr/info2.htm

Search criteria:
"Waltzing Matilda" "Australian Open"
“Tina Arena” “Waltzing Matilda”


I hope this provides you with the information you are seeking.

Best regards,

Bobbie7-ga

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Request for Answer Clarification by dlsinclair-ga on 12 Aug 2002 06:42 PDT

It was definately a group, not a soloist.  This is not the performance
I am looking for.

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Clarification of Answer by bobbie7-ga on 12 Aug 2002 06:54 PDT

Ok, I will attempt to find that information for you and post another
answer.  Thanks for the clarification!

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Clarification of Answer by bobbie7-ga on 12 Aug 2002 08:01 PDT

I've done more research on the subject including Usenet message
boards and haven't been able to come up with any group, only to Tina
Arena.

Search Criteria in Google Groups:
http://groups.google.com/groups?q=%22waltzing+matilda%22+%22Australian+Open%22&ie=UTF-8&oe=UTF-8&hl=es&btnG=B%C3%BAsqueda+en+Google

Could it have possibly been the seekers? They performed at the 1994
AFL Grand Final.
http://www.geocities.com/SunsetStrip/Alley/4567/

In addition, I’ve sent out an e-mail inquiring for the group you refer
to. As soon as I receive an answer I will get back to you.

Would you have any other information to go on? 

Thank you

I received this response today from Roger (he has the very complete
Waltzing Matilda Website): "I vaguely remember there was a bunch of
relatively clean-cut, 'nice' young men around at the time. 
Unsurprisingly, they didn't last long, and I doubt if many people can
remember them."
When I receive more replies from my e-mail inquiry, I will post them
for you.
--bobbie7-ga--

The Pogues covered Matilda back in the 90's.