Dan Fogelberg does this with open G tuning of some kind, but I can't figure that out, but here are some
chords that fit well, and can be capo'ed to fit most vocal ranges.
Intro: One verse instrumental
C Dm Em F
Longer than there have been fishes in the ocean
C Dm Em F
Higher than any bird ever flew
C Dm Em F
Longer than there've been stars up in the heavens
D# Dm C F G(bar'ed)
I've been in love with you
C Dm Em F
Stronger than any mountain cathedral
C Dm Em F
Truer than any tree ever grew
C Dm Em F
Deeper than any forest primeval
D# Dm C
I am in love with you
[ Tab from: https://www.guitartabs.cc/tabs/d/dan_fogelberg/longer_crd_ver_4.html ]
Bb F G# D#
I'll bring fire in the winter
Bb F G# D#
You'll send showers in the spring
Bb F G# D#
We'll fly through the falls and summers
G G7
With love on our wings
C Dm Em F
Through the years as the fire starts to mellow
C Dm Em F
Burning lines in the book of our lives
C Dm Em F
Though the binding cracks, and the pages start to yellow
D# Dm C
I'll be in love with you
D# Dm C
I'll be in love with you
D# Dm C F - G
C Dm Em F
Longer than there have been fishes in the ocean
C Dm Em F
Higher than any bird ever flew
C Dm Em F
Longer than there've been stars up in the heavens
D# Dm C
I've been in love with you
D# Dm C
I am in love with you
D# Dm C
