Anything apart from the two mainstream default harmonicas (Solo-tuned fully-valved chromatic, and un-valved Richter 10-hole diatonic). Alternate tunings, different construction, new functionality, interesting old designs, wishful-thinking... whatever!
The other day I thought that maybe I had penciled out a new tuning. When I checked Pat Missin's catalog, I found that it was already known as Variation 2.5a of Dorian Cross.
2.5 - DORIAN CROSS
BLOW C E G C E G C E G C
HOLE 1 2 3 4 5 6 7 8 9 10
DRAW D G Bb D F A Bb D F A
2.5a - VARIATION OF 2.5
BLOW C E A C E G C E G C
HOLE 1 2 3 4 5 6 7 8 9 10
DRAW D G Bb D F A Bb D F A
What I wish to point out here is that this tuning, which features an F major scale, would be a really nifty re-tuning of a stockPaddy Richter Kongsheng Baby Fat. The result is a major scale with three notes below and four notes above. Pretty cool!
2.5a - VARIATION OF 2.5 -- truncated
BLOW C E A C E G C
HOLE 1 2 3 4 5 6 7
DRAW D G Bb D F A Bb
Of course, this is still a Dorain machine sporting four notes below the scale and three above. And in the relative Dmin, this harp has one note below the natural minor scale and six above.
Now let us compare the last re-tuning in the post just above with this re-tuning of a Paddy Richter Baby Fat:
BLOW C E A C E G C
HOLE 1 2 3 4 5 6 7
DRAW D G B D F# A B
The tuning called var. 2.5a is in F major, with the first tonic available as a full bend of the 2 draw.
The re-tuning shown in this post is in G major, with the first tonic as a regular 2 draw note. This is essentially the first seven holes of Melody Maker. Having this tonic be a regular draw note is arguably an advantage because it is easier to play.
However, if we also value the notes just below the first tonics, then var. 2.5a has its own distinct advantage. All of its major scale notes are either regular blow/draw notes or (in the case of the first tonic) a full bend. In the Melody Maker re-tuning, playing the F# just below the first tonic requires a partial bend. From the standpoint of intonation, this is more difficult.