ROLLING STONE:
Lady Gaga whoops through "The Lady Is a Tramp" with such gusto, you can hear Bennett grinning.
NEW YORK TIMES:
“The Lady Is a Tramp,” with Lady Gaga, is a playful give-and-take of improvised remarks, in which she displays her considerable chops as a hard-edged pop-jazz singer.
NEW YORK POST:
The album's best pop moment is when Bennett shares the mike with Lady Gaga for “The Lady Is a Tramp.” In this love ballad Bennett sounds elegant in his croon and Gaga is sassy and swank in her conversational delivery. There’s no doubt that on this duet Lady G. is a tramp for Tony.
AOL MUSIC:
Gaga showcases her powerhouse vocals and signature theatricality in this playful pair-up with Bennett.
WALL ST JOURNAL:
Lady Gaga is amazingly likable, and not at all trampy, on "The Lady Is a Tramp."
LA TIMES:
Some of these May-December cuts sound great, particularly Bennett and Gaga’s “The Lady Is a Tramp,” in which he can’t stifle his amusement with her drama-kid shtick. (“I love to rowboat with you and your wife in Central Park Lake,” Gaga ad-libs pricelessly.)
THE GUARDIAN:
Soaked in old-world schmaltz, its treats include a hilariously spirited version of "The Lady is a Tramp" with Lady Gaga in wisecracking dame mode.
NEWSDAY:
...his playful banter with Lady Gaga, who also gets to show off her impressive voice, in "The Lady Is a Tramp."
ASSOCIATED PRESS:
Bennett wisely doesn't treat the Great American Songbook as a museum piece, which serves him well on the opening duet with a flirtatious Gaga on the Rodgers and Hart tune "The Lady Is a Tramp," with a brassy big band swing arrangement. Bennett chuckles as a sassy Gaga alters the lyrics ("This chick is a tramp"), affects a Brooklyn accent, throws in updated references to the Yankees, and even scats briefly, but in the end she leaves no doubt about her impressive vocal chops.
THE TELEGRAPH:
The opening credits roll to a big, brassy, banter-packed backslapper in which 85-year-old Bennett and 25-year-old Gaga caper through The Lady is a Tramp: the underclad dame really can sing and has fun.
NEW YORK MAGAZINE:
The Lady has the sassy, slightly show-tune-y voice down cold. It works! Unless Gaga decides to pay tribute to Disney's Lady and the Tramp with the costuming (we fear dog suits), this collaboration can go in the "success" column.
IDOLATOR:
We all know Gaga has no problem belting out a show-stopping number, but damn if we aren’t surprised just how effortless the pop star sounds crooning this classic showtune. Hear their duet below.
REUTERS:
Lady Gaga is a perfectly engaging vamp on the album's opener, “Lady Is a Tramp."
USA TODAY:
While the material is classic, he and his partners give the impression that singing together is a genuine pleasure. That sense of fun certainly shines through as he trades lines with Lady Gaga on a swinging The Lady Is a Tramp
SEATTLE TIMES:
The swinging big-band opener with Lady Gaga, "The Lady is a Tramp," absolutely sparkles.
. Jazz all sounds the same to me. 
