Q: What is a bass harmonica?
A: Extending the description in part 1 and from "Bass Harmonica" 30 Aug 94 WY:
Hohner Bass No. 265 is a two octave instrument, Low E (same as on a bass guitar) and two octaves up. All the notes are blow, and have second reeds tuned an octave higher to give the note more bite.
There is an Extended Bass (Hohner No. 268) that goes on up to C a sixth above the high E on the regular bass. This is a HEAVY instrument.
The Bass is actually two separate bodies, with one placed above the other, with the two held together by hinges on both sides, allowing you to angle the two mouthpieces in towards each other, or out away from each other.
The bottom row has all the natural notes - it's just a C major scale, running from E to E.
The top row is not in C# as you might expect. It's in Gb. Why?
Well, the primary activity in most simple bass lines is to play the root and the fifth of the chord. it's easier to move between these notes if they're on the same row. Most chords have perfect fifths. The C scale does not give you a perfect 5th above B (F is a diminished 5th). B doesn't even occur in the C# major scale, so this would be a poor choice. The B major scale would not give you a perfect 5th on (or Bb), so that's out, too.
It just happens that the C scale and the Gb scale in combination give you all the perfect 5ths on one row or the other.
here is the layout for the regular bass:
F Gb Ab Bb B Db Eb F Gb Ab Bb B Db Eb
E F G A B C D E F G A B C D E
Note how the hole placements are staggered, to put the flat/sharp notes in between the natural notes.
Both F and B are duplicated. The Extended bass continues this pattern up to concert Middle C (written an octave higher - bass and guitar are both written an octave higher than they sound) -- "Bass Harmonica" 30 Aug 94 WY