Sean Lennon releases a never-before-heard song that he wrote with Carrie Fisher.

Sean Lennon releases a never-before-heard song that he wrote with Carrie Fisher.

Sean Lennon, son of John Lennon and Yoko Ono, just released a never-before-heard song he co-wrote with the late Carrie Fisher.

Lennon, who was very close Fisher, noted that the two wrote "Bird Song" years ago, but he was inspired to share it with the world after Fisher's death. Fisher provided the lyrics while Lennon wrote the music, and Willow Smith even lent her vocal talents to the song. He released the hauntingly beautiful tune on his SoundCloud on Sunday.

Carrie and I wrote this song years ago. When she died I just felt I had to record it. This is only a demo unmixed, we only had a few hours to record it. But the lyrics she wrote with me I think are marvelous. Carrie and I used to stay up til dawn chatting and pontificating about life. They were my best moments. Anyway... we wrote a song about staying up too late and hearing the birds sing. Willow Smith is a prodigal angel and was generous enough to lend her golden voice to this little tune.

Lennon also provided a text copy of Carrie's lyrics along with the unmixed song.

Love comes on cat's feet
It circles the corners
It sits by the window and whispers...
'Mine! Your mine! all mine!'

My arm fell asleep
And dreamt it was your arm
Hush lest we break the spell, oh well, oh well..

It's all so wrong
To greet the dawn
The birds sing that awful song saying
'You don't belong here!'

After Fisher passed away in 2016, Lennon posted many tributes to the woman he called "one of the best and closest friends I’ve ever had in my life." In the caption of this picture of the two together, Lennon wrote that he hopes Fisher would be reunited with all the artists she loved who have also passed away, adding "and I hope my dad greeted you at the door."