Ysgol Glanaethwy performed in both Welsh and English on the show
Two choirs from north and south Wales will compete with one from east London in the grand final of the BBC talent show Last Choir Standing.
The three were left after Saturday's BBC One semi-final saw ACM Gospel Choir from Guildford, Surrey, knocked out.
Ysgol Glanaethwy from Bangor, Only Men Aloud! from Cardiff, and Revelation will sing for the title on Saturday.
Fans of the remaining choirs can see them perform in public in or near their home areas on bank holiday Monday.
The trio have been whittled down from 60 choirs across the UK who were invited to audition after thousands of people applied to the programme.
The four remaining on Saturday had staged a joint performance of Beyonce's One Night Only, before each sang three songs.
Members of ACM Gospel Choir come to terms with news of their defeat
A viewers' vote saw Only Men Aloud! and Revelation make it through to the final weekend.
Then it was up to the three studio judges to decide between ACM and Ysgol Glanaethwy.
Actress Sharon D Clarke and tenor Russell Watson both backed Ysgol Glanaethwy, which spelled the end for ACM even before the third judge, choral director and conductor, Suzi Digby, had revealed her choice.
Only Men Aloud! was begun in 2000 in Cardiff by Tim Rhys-Evans who wanted to create a young male voice choir unafraid to tackle music not usually performed by traditional male voice choirs.
Revelation was the brainchild of Nick Bowers-Broadbent 10 years ago when he began teaching at St Bonaventure's School in Forest Gate, east London.
Ysgol Glanaethwy was started 18 years ago in Bangor by Cefin and Rhian Roberts, who felt local children were not getting enough performance training.
Only Men Aloud! will go on to the grand final next weekend
The finalists will be performing at various locations on Monday.
Only Men Aloud! can be seen at Mermaid Quay, Cardiff Bay (1245 BST); Revelation outside the National Theatre, London South Bank (1630 BST); Ysgol Glanaethwy at their Bangor school (1100 BST) and at the Faenol Festival, Bangor (1900 BST).
The public will decide the ultimate winner in two programmes on Saturday night.
The final of Last Choir Standing will be on BBC One on Saturday, 30 August (1800 and 2050 BST).