The singer and former Destiny's Child member gave fans a preview of the tune on Instagram, along with a photo of her little bundle of joy being cradled.
In the short clip you can hear the 33-year-old singing, "You will always be mommy's little baby."
The track was produced by Verse Simmonds and The Order and is available to listen in full on the singer's official SoundCloud page.
"There's no better feeling than holding my beautiful nephew," Bey wrote. "I thank god for the honor of witnessing my sisters journey into motherhood. I've always dreamt of our little ones growing up together. I'm so thankful for our bond. Baby Ty, I love you so much. Congrats to my Spoons."
"She's doing very well," she told us. "Kelly's going to be an amazing mom. She's always been great with children. She loves babysitting, she loves buying stuff for kids. She has such a big heart. She's a giver and a nurturing person and, really, that's what motherhood is all about."