OK, here's my attempt at a transcription from Almeda Riddle's recording on Southern Journey Volume 7 (I don't have the CD booklet).
-Joe Offer-

RAINBOW MID LIFE'S WILLOWS

Last night I dreamed of my true love
All in my arms I held her
But I awoke, she was not there
Now I must live without her

Her yellow hair, like strands of gold
Was streaming over my pillow
Oh, she's the only one I love
My rainbow mid the willow

I searched for (far?) high and I searched for low
And I made some low inquiries
But they all said, "No, we've seen no such
We would have no such in our keeping"

But when she heard from me those words
She whispered low at her window
"Oh darling I'd be in your company
But locks and chains doth hinder"

Now when I heard those words of hers
I swore that room I would enter
Or I would (prayer???) know the reason why
She was locked and chained within there

Up stepped her father, stern and wise
Likewise two stalwart brothers
"Before you enter that locked room
In your life's blood you'll wallow"

They've taken away my own true love
And tears now wet my pillow
Oh, she's the only one I love
My rainbow mid life's willow


(from the singing of Almeda Riddle)

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I transcribed what I heard, and I think I have it down quite well - Riddle sings quite clearly. I have no idea what that word is in "I would ... know the reason why." sounds like "prayer," but that doesn't make sense. as for searching, it sounds like "I searched far high and I searched far low" to me.
It's a great song.
-Joe Offer-