Jennifer Lopez is putting the "happy" in happy birthday!

In celebration of Lopez turning 55 on Wednesday, July 24, the singer and actress joined her longtime friend and vocal coach Stevie Mackey for a special rendition of a classic Judy Garland and Barbra Streisand mashup.

The pair shared the clip to Instagram on the morning after Lopez's big day, featuring Mackey and Lopez going back and forth on Garland and Streisand's iconic "Happy Days Are Here Again / Get Happy" performance.

Seated on a big couch together as Lopez rocked a sheer dress and a pair of dangly earrings, the duo took turns for their new cover — with Lopez singing lines from "Happy Days Are Here Again," while Mackey handled the "Get Happy" portion of the performance. While Mackey sang lines like "Forget your troubles, c'mon get happy," Lopez stuck with "Happy days are here again, the skies above are clear again."

Both singers smiled at each other throughout the performance, and Lopez captioned the joint upload with: "Here’s to a new and HAPPY year around the sun… Late birthday nights with @steviemackey."

Garland and Streisand debuted their "Happy Days Are Here Again / Get Happy" mashup during an October 1963 taping of The Judy Garland Show. The performance itself has since been released multiple times by Streisand, including on her 2002 Duets album.

As for Lopez, the "Can't Get Enough" singer marked her 55th birthday by uploading a message to fans this week, as she shared a few behind-the-scenes snaps of an at-home celebration featuring a blue cake, several bouquets of flowers and her wearing a blue silk pajama set.

"I’ve been seeing all of your birthday wishes, beautiful videos, and posts all last night and this morning from all over the world. I have laughed, smiled, shed some tears, and when I saw the billboard in Times Square, I was completely overwhelmed," Lopez wrote, referring to a "Happy Birthday Jennifer Lopez" sign that appeared in Manhattan. "I really do have the best, most amazing fans in the world. I could never express how moved I am or how incredibly blessed I feel to have all of you be a part of my life. Thank you sooooo very much. 🤍🙏🏼,"

 "It’s hard to believe we have spent all this time together. It’s funny as I sit here contemplating on the most extraordinary journey I still feel like the same girl starting out so full of energy and bravado, so ready to take on the whole world on the outside and yet so tender, fragile and sometimes frightened but always full of love on the inside," she added. "I have so much love for you." 

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Lopez then shared a thoughtful statement with her supportive fans: "YOU are my biggest gift."

"Besides my family and friends, you have always been there for me in the good times and in the tough times. I can always count on you," Lopez wrote. "And I want you to know that you can always count on me. Thank you for your caring, your understanding, your loyalty and most importantly your love. 🤍"

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Lopez also gave fans a peek at the Bridgerton-inspired party she held in the Hamptons on Saturday, July 20, when she uploaded a video montage of some of the party's 19th century attire. "Dearest Gentle Reader… And a splendid evening was had by all," she wrote in the video's caption.

Among those in attendance were Lopez's mom Guadalupe Rodríguez, who arrived in some period-appropriate attire. Multiple sources confirmed to PEOPLE that Lopez's husband Ben Affleck was not in attendance, marking another significant milestone apart for the two, following their second wedding anniversary earlier in the month.

As Lopez and Affleck, 51, have remained on separate coasts in recent weeks, Lopez has still spent some quality time with Affleck's daughter Violet, 18, in the Hamptons — having been spotted this month on a bike ride and even getting some shopping in.

"Her summer isn't exactly what she originally had planned, but she's making the best of it," a source recently told PEOPLE. "She's always grateful for family time."

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