No, there isnt a secret musical in the series finale.
Its a fitting song for Alice (Reynolds) and Robin (Skovbye).
Below, the actresses discuss what being part of this show has meant to them.

Jack Rowand/ABC
What has it meant to you to play these characters?REYNOLDS:A lot.
Its meant that I can just not worry about making mistakes in a way.
Can you show me the ropes?
Can you help me?
Its that thing of people working together, hope, optimism, and kind of paving the way.
It doesnt end withOnce Upon A Time, I dont think.
I think it just wont stop when the series wraps on Friday and when it airs in May.
You go home, you retire.
I think thats really important in a world that can be kind of heartbreaking at times.
To know that nothing is certain and that the world and your life is ever-changing is really comforting.
We want to make it about our children, so its the next generation.
That would be really interesting.
Do you have a new affinity for fairy tales after being on OUAT?REYNOLDS:Yes.
Yes, very much so.
You get to relate a bit more to the real world character, but then escape into fairy tale.
That will always be a massive thing for me.
Were part of helping fight this curse and I just think thats so cool.
What was it like having the final love story of the show?REYNOLDS:Is it?
Im not sure about that.
Theyre going to find us out.
I never expected that when I started.
Theyre going, Its like we never left.
How would you describe the finale?REYNOLDS:I think theres something for everyone in the finale.
Everyone can take away something thats really personal to them.
I think theyll take something thats real away from it.
which is really cool and really special.
I wasnt expecting Henry for some reason.
Wish Rumple coming back, its just that thing of redemption.
We were seeing someone go through such a journey to see a mirror of that evilness come back.
That was something I wasnt prepared for.
I felt like we had an affiliation.
Originally I thought maybe that Rumple might be my dad.
Thats why were so connected.
Theres a gorgeous scene in the final few scenes of the final episodes.
Oh god, [emotionally] drained.
Alice and Robin have ventured to Storybrooke to seek help.
Im gonna steal your truck!
Its not plain sailing from there.
Figure out how to get these people to help us.
Theyre going about their business, but things have changed in Storybrooke a little bit.
Its not all rainbows and peace anymore.
Also, because we come going, You know, that isnt Henry.
Weve got another Henry.
Were putting all this stuff in their mind.
No one trusts or believes us.
And if this curse goes through, it just destroys everything they built.
I said to mum and all the family, A couple more months, guys.
Ill try my luck in L.A., because Ive never done anything like this before.
Ill try my luck and see what happens in L.A. and then go from there, really.
Once Upon a Times series finale airs Friday at 8 p.m.