The celebration is planned for the final match on home soil before the Wales' team that face the Baa-Baas leave for their three-Test, four-match, tour of Australia.
The choir will assemble in the north stand of the stadium where they will be conducted by the stadium's feature choirmaster, Haydn James, and accompanied by Symphonic Brass Wales.
The choir will unveil a medley of songs which Haydn James is preparing to honour the countries represented by the players in the Barbarian line-up.
Fans will be able to hear the massed choir from 1.00pm which is precisely one hour before the kick-off.
Supporters will be encouraged to join in the singing to ensure the capital city echoes to the sound which will boom out across Cardiff.
The massed choir will also strike up during the match to raise the noise level to a massive intensity as the game unfolds.
Alex Luff, who manages pre-match entertainment at the Millennium Stadium, said: "The traditional sound of Welsh rugby will be at its best when Wales face the Barbarians this summer with a 1,000-strong choir booked to boost the decibels at the Millennium Stadium.
"Welsh rugby fans are renowned for their passionate singing when Wales take on the opposition at the home of Welsh sport and we are expecting an extra special sound for the final home clash before Wales embark on their tour of Australia."
Tickets priced from £25 for adults and £10 for under 16s can be purchased online at www.wru.co.uk/tickets or by calling the ticket hotline 08442 777 888 or Ticketline on 02920 230130.
The full list of choirs is as follows:
Cwmbrân Male Choir, Cor Meibion Taf, Beaufort MVC, Caldicot MVC, Aber Valley MVC, Bridgend Male Choir, Gwalia Male Choir, Treorchy Male Choir, Cwmbach MVC, Dowlais Male Choir, Cambrian Male Choir, Cor Meibion Abercynon, Cor Meibion Morlais, Cardigan Rugby MVC, Cowbridge MVC, Neath MVC, Kenfig Hill MVC, Cor Meibion De Cymru, Cor Meibion Dyffryn Aman, Pendyrus Male Choir, Llanelli MVC, Morriston RFC MVC, Glyneath MVC, Treharris MVC