What key should I buy my harmonica in if I'm trying to play with an Appalachian Dulcimer? I've heard C and D?

Simple answer - G

More complicated answer:

Some good advice there for playing along with guitars and such but not so helpful really for dulcimer play-along. Here's why:

The Appalachian Dulcimer is a diatonic instrument with a mixolydian scale fretboard on the open string. When tuned to DAd or DAA (typical) it plays in D major (regardless of the key of the tune). When tuned in DGd (not uncommon) it plays in G. And, if tuned to DAc (for minor modes) it's in Dmin. The dulcimer "can" be played in other keys but reality is simply that it's not very often done because it requires retuning the strings. That's one of the limitations of a diatonic instrument just as it's a limitation of the harmonica.

So, it would appear that the answer would be "get a harp in D" but that's not exactly right. Harmonica is a diatonic with an ionian scale. If you want to play in D mixolydian (like a dulcimer with no 6 1/2 fret tuned to DAd) then you do it from second position of a G harp since D mixolydian has the same key signature as G major. If your dulcimer is tuned to DGd then that's G too and you play your harp from first position. (the C harp would work for this in second position playing in G as well) If the dulcimer is playing in DAA from the 3-fret then you're in D ionian scale and will need a D harp for that one or will avoid the 7th (C/C#) in first position from a G harp.

What about DAc in a minor mode? You need an F harp on which you'll play from D (4th position) or a harp in the minor mode (Aeolian/natural minor or Dorian) the tune is in.

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Good models:

Hohner Marine Band, Special 20, or Golden Melody. Assuming you're going to be doing tune playing and not blues vamping (Appalachian Dulcimer isn't really a blues playing instrument) then the Golden Melody is a pretty good choice. For a particularly cool sound together, the Hohner Echo Celeste is a nice choice.

An extra note: The harmonicas marked "country tuned" are simply mixolydian mode diatonics and are exactly the same scale as a mountain dulcimer's fretboard. If you can find one - you'd play one with the same key as your friend's melody strings (usually D) and play it straight harp.

What works best with a dulcimer (and general for any tune playing) is a solo-tuned diatonic harmonica such as the Marine Band 364-S or the Asian tremolos. Because you aren't missing notes below the root that a Richter tuned (blues harp) harmonica has from holes 1-4. This one, for example, http://www.harmonicastore.com/product/hohner-marin... but, if you're going to spend that sort of money - you might as well get a chromatic harmonica and solve that whole diatonic scale problem.

Visually: The notes of the scales in D mixolydian and G major/Ionian are:

D E F# G A B C D

G A B C D E F# G

notice those two scales have exactly the same notes - they just start in different places. His dulcimer is mixolydian, your harmonica (unless you buy a "country tuned") is ionian.

I know, TMI and some confusing music theory. Probably why you don't see dulcimer and harmonica together too often.

It depends on what key whatever song you're playing is in. Even if a dulcimer is tuned in open C, your friend could play a song in D, then you have the wrong harmonica. Just get a blues set or a major set. Suzuki is a bit cheaper than Hohner for a set. You really need a set for an ensemble unless you plan on making every song in the same key.

Depends what key the song is in. If the song is in the key of C start with a C harmonica or F harmonica, If the song key is G then G harmonica or C harmonica, song key D then D or G harmonica.

Key of D and possibly and even an E

Instrument brand: 10 hole Hohner Marine Band

Good book to buy: Blues Harmonica, by Tommy Morgan, Gwyn Publishing Co., 1971.

The key you use is ALWAYS dependant on the song key and your technical abilities.

Diatonic harmonicas can be played chromatically so you can use ANY key harmonica for any song.

Notes are Notes.

Bernice Gertrude