Hudson was a last-minute addition to the World Health Organisation's livestream concert, which was billed as a H.E.R. Instagram Live showcase from her home.
The Oscar-winning "Cats" star kicked off the virtual all-girl gig with a performance of "Hallelujah" and Sam Cooke's "A Change Is Gonna Come" before H.E.R. offered up mellow vibes by performing Daniel Caesar's "Best Part" and her rendition of John Mayer's "Daughters" - a fan-requested tune.
Speaking into the camera, she said, "I think the people, we're the real virus. I'm happy we have this, so we're not all at home feeling alone."
The Hudson & H.E.R. performances were staged to raise awareness and funds for the Global Citizen campaign and the WHO's Solidarity Response Fund.
Joe Jonas was also among the livestream concert highlights on Wednesday as he took to Instagram to host a surprise 80s party from his home.
Miley will be back on Thursday to talk to Ryan Tedder and Mark Ronson at 2.30pm EST (https://www.instagram.com/mileycyrus), while other highlights for the day include a Diplo country-based DJ set on YouTube and Instagram at 10pm EST (https://www.instagram.com/diplo), and Vanessa Carlton's ongoing two-song daily set from 6pm EST (https://www.instagram.com/vanessacarltonactual).