The song of the week is 'Worried Man Blues' in the key of Bb.
The Carter Family - key of Bb
Flatt and Scruggs - key of G
The Stanley Brothers - key of A
On the Carter Family and Flatt and Scruggs recordings, the chord progression is:
On the Stanley Brothers recording, the chord progression is:
If one is paying attention only to the lyrics when comparing the different versions of the song with each other, it would seem that to arrive at the 12 measure version (Carter Family/Flatt & Scruggs), you just omit the third line of the 16 measure version (Stanley Brothers). However, if one pays attention to the melody and the chord progression, then it becomes clear that the 12 measure version omits the second half of the second line and the first half of the third line of the 16 measure version rather than the whole third line of the 16 measure version. In this regard, notice the differing number of measures of the '4' chord in the 16 measure and 12 measure versions.
When I lead the song at the jam, I almost always use the 12 measure version, but be prepared for the 16 measure version to show up occasionally when other people lead the song at the jam. On the attached melody sheets I have shown the relation between the longer and shorter versions.
The Key of Bb
In the key of Bb: 1=Bb, 4=Eb, 5=F
The notes that make up the Bb chord are Bb, D, and F.
The notes that make up the Eb chord are Eb, G, and Bb
The notes that make up the F chord are F, A, and C.
Together, these notes form the Bb Major Scale: Bb, C, D, Eb, F, G, and A.
The melody of Worried Man Blues uses only 6 of these notes: Bb, C, D, F, G, and A, which so happen to be the 6 notes that the Bb Major Scale shares in common with the F major scale (F, G, A, Bb, C, D, E).
If you are fiddler or a mandolin player, and you already play songs or licks in F, then, provided that these songs or licks do not require using the 4th string, you can take your same fingerings for F and move them all one string lower in pitch, and you will be thereby be playing in Bb.
For playing chop chords on the mandolin that use no open strings, if you move the chords shapes you use for playing in the key of A up by one fret, this will put you in the key of Bb.
For playing in the key of Bb, bluegrass banjo and guitar players almost always capo to the 3rd fret, so that they can use the same fingerings that they would use for playing in the key of G. (In the key of G: 1=G; 4= C; 5=D.)
Banjo players will need to raise the pitch of the fifth string to a Bb note (registers as A# on most tuners). This is done by capoing (with a 5th string capo, or 8th fret spike) the 5th string at the 8th fret. For banjo players who do not have a fifth string capo or an 8th fret spike (that includes myself), spike the 5th string at the 7th fret, and then tune it up a half step to a Bb (A#) note. This is best done by ear by playing the 5th string with the thumb while playing the 3rd string with the index finger, turning the 5th string tuning peg slowly until the 5th string sounds harmonious with the 3rd string.