The jazz singer, who teamed up with the 'Applause' hitmaker to surprise more than 700 students with a music master-class in New York yesterday (16.06.14), admits he was blown away by her talent when he was introduced to her music.
Speaking at the Frank Sinatra School of the Arts in Astoria, Queens, he said: ''When I first heard Gaga sing my reaction was that she is going to be bigger than Elvis. She is so bright and intelligent and she has it. In jazz you either got it, the syncopation, the rhythm or you don't, and when I heard Gaga I said, 'She's got it!'''
Tony, 87, founded the school in 2001 and it has gone on to become one of the most successful performing arts centres in the city, helping to nurture talent and create future stars.
Gaga, 27, also gushed about the legendary singer and told students: ''When I am with Tony I feel like I am 15 years old at home listening to Ella and Coltrane records.
''The way he sings is effortless and so prolific. It's so liberating to be able to sing jazz, especially at this point in my career!''
The pair performed a number of classic American songs during the surprise session, including 'The Very Thought of You' and 'Every Time We Say Goodbye'.
They then serenaded each other and danced to 'I Can't Give You Anything But Love'.
The season 7 premiere guests featured some cast members we haven't seen much of for a while.
This year's Rotterdam event was definitely one to remember.
New album 'Flower Boy' comes later this summer.