When the "Poker Face" hitmaker confirmed her residency at the Park Theater inside the Park MGM Las Vegas hotel last year (2018), she revealed she would be putting on different shows on different dates - with the majority of her residency comprising of the pop-orientated "Enigma" concert and four dates being her Jazz & Piano show, featuring "stripped-down versions of her hits as well as music from the 'Great American Songbook'."
GaGa kicked off the "Enigma" part of her residency in late December but made her Jazz & Piano debut on Sunday night, and brought her jazz collaborator and good friend Bennett along for support.
In fan footage posted on social media, the Oscar-nominated singer, dressed in a skintight bejewelled dress, told the audience, "Ladies and gentleman, we have a special guest tonight. I wonder who it is?... Ladies and gentleman, the one, the only, the legendary Mr. Tony Bennett!".
The crowd went wild, screaming as the veteran crooner walked on stage and gave GaGa a hug, before they launched into "Lady is a Tramp" and a rendition of "Cheek to Cheek", the title track of their 2014 joint jazz album, which they toured together in 2015.
Bennett, who also attended her "Enigma" show on Saturday, wasn't the only collaborator at her concert - GaGa also recruited her good friend, trumpeter Brian Newman, who worked on the "Cheek to Cheek" album, to serve as bandleader for her 30-piece orchestra.
She kicked off the night with "Luck Be a Lady", taken from the musical "Guys & Dolls", and covered classic tracks such as "La Vie En Rose", which she sings in 2018 film "A Star Is Born", as well as "Anything Goes", "Fly Me to the Moon" and "New York, New York", while also doing stripped-back versions of her songs "Poker Face", "Born This Way", "Paparazzi" and "Bad Romance".
The remaining Jazz & Piano dates take place on February 3 and 2 and June 9.