They'll Know We Are Christians:
I have also seen them play it on guitar.  It sounds good.
Banjo intro:

E----------------------------------|
B----------------------------------|
G----10------10-----10----10-------|
D-------12------12----12----12-----|
A-12-------12-----12----12---------|
E----------------------------------|

E--------------------------------------|
B--------------------------------------|
G---3---3---3----3---------------------|
D--5---5---5----5----------------------|
-A-5---5---5----5----------------------|
E--------------------------------------|

Chords:
 Dm
We are one in the Spirit
 Gm
We are one in the Lord
 Dm
We are one in the Spirit
 Gm
We are one in the Lord
Dm                          Gm
And we pray that our unity may one day be restored
Bb                                Dm
And they'll know we are Christians by our love, by our love
     Gm                                Dm
They will know we are Christians by our love

Guitar:
Dm                Dm
Banjo:
E----------------------------------|
B----------------------------------|
G----10------10-----10----10-------|
D-------12------12----12----12-----|
A-12-------12-----12----12---------|
E----------------------------------|
Guitar:
Gm                Dm
Banjo:
E--------------------------------------|
B--------------------------------------|
G---3---3---3----3---------------------|
D--5---5---5----5----------------------|
-A-5---5---5----5----------------------|
E--------------------------------------|
 Dm
We will work with each other
 Gm
We will work side by side
 Dm
We will work with each other
 Gm
We will work side by side
 Dm
And we'll guard each mans dignity
 Gm
And sing each mans pride
Bb                                Dm
And they'll know we are Christians by our love by our love
     Gm                                 Dm
Yea they'll know we are Christians by our love

Guitar:
Dm                Dm
Banjo:
E----------------------------------|
B----------------------------------|
G----10------10-----10----10-------|
D-------12------12----12----12-----|
A-12-------12-----12----12---------|
E----------------------------------|
Guitar:
Gm                Dm
Banjo:
E--------------------------------------|
B--------------------------------------|
G---3---3---3----3---------------------|
D--5---5---5----5----------------------|
-A-5---5---5----5----------------------|
E--------------------------------------|

God Bless,
Byron