Harmonica/Music Style

Classical
There are no discussions as to what harmonica to use: Only the following are appropriate, nothing else:
 * Chromatic harmonica
 * Chord harmonica (for chord parts)
 * "Polyphonia" type for quick runs (e.g.: Flight of Bumblebee)
 * Bass harmonica for low-range sound.
 * Horn harmonica if asked for; however, the role is typically filled in by Chromatic harmonica.

Classical music is all about technique and following the sheet music while showing an understanding of the actual music underneath the written notes (such as Bach's special vibratos/tremolos).

If you decided to play your style, you definitely are not doing classical. If you play a classical piece in a blue style or rock style, you are playing it as blues or rock — you are not playing classical music.

Jazz
While Jazz songs require that you play them chromatically, luckily, they do not require the exact tonal precision like classical music. This makes it acceptable to play with bends and overblows.

In Jazz, the instruments vary quite a bit; the jazz group I play with consists of nothing more than guitar, keyboard, and double bass, and a djembe. The harmonica's purpose can also vary from playing the main melody to accompaniments, riffs or even playing chords. In fact they may even play music of all kind, from blues to rock to bluegrass (or even zen-influenced temple music)!

Thus, if possible, bring ALL twelve keys of diatonic harmonica AND chromatic harmonica, and pick the harp for the following reasons: If you can bring only one harp bring a chromatic (or XB-40 if possible) since it can approximate a majority of the aforementioned decisions, if not all. Of course, if one believes that his overblow or bending is perfect for every songs they will play, then bring whatever harp(s) they think is best.
 * key of the songs, and number of key switch: If it's too much to handle on one harp, either due to hole-arrangement of the harmonica or the complexity of the song, switch to another one. Also, don't just stick to "positions"; if it seems better to use overbends and bending for the note instead of switching holes, then use such method.
 * mood and tone of the song - if a song require perfect intonation, grab a chromatic; if it seems best to be bluesy, then pick a diatonic. (unless you're an expert at bending the chrom)
 * Role of the harp: Is it mainly for accompaniment or to provide main chords or melodies?

Due to the fact that jazz is quite horn oriented, the most common keys in a jazz band are F, Bb, and Eb. However, it is still played chromatically. Thus one can either purchase harps (chromatic or diatonic) in those keys, or play them in crossharp, and thus get harps in Bb, Eb, and Ab. Eb and Bb are especially useful in this sense. Regardless, one has to play it with overbend and bending. Since C is still easier to purchase, especially for 16-holes, in my humble opinion, it would be even better to just practice on a C harmonica if you are using the chrom.

Bluegrass
In Bluegrass, the traditional instruments used are as follow: As Mike Stevens called it the "pneumatic fiddle", harmonica's role is the same as a fiddle. Also, in his opinion, it is best to use a normal C-major diatonic and then use overblow to get all the notes needed. with practice, it is actually possible to make it sound like a fiddle; just listen to his record.
 * fiddle
 * banjo
 * acoustic guitar and/or resonator guitar
 * mandolin
 * upright bass

Bluegrass music is quite complicated, since it is very common to play it chromatically. Even worse, bluegrass do require an exact tonal requirements similar classical musics. As Pete Wernick, former President of International Bluegrass Musician Association, had stated, people don't like *fast* harmonica playing in bluegrass, which is being seen as "huffing and puffing" that distracts from the pure sounds of the picked and bowed instruments. However, bluegrass seems to mind less on slower, wistful tunes where harmonica can add a beautiful, evocative feel.

What he stated is of follow:
 * 1) Some people will like it, some won't.
 * 2) In a jam session, choose where you're welcome and leave where you're not.
 * 3) To be more generally welcome bring and be able to play another, more wanted instrument.
 * 4) Choose your situations carefully. Don't bring out the harmonica until a slower song comes along. Even then, play it with good tone and feeling but no excessive emotional expression and no attention-seeking.. That will create a great first impression and good reaction. Then put it away until the next opportunity where you know it will go over well. Don't start "chancing" to use it on more questionable songs (especially faster ones) unless you really think it will work.

My personal opinion: Any harp is fine, as long as you can hit the note spot-on. That means, no blues notes, no wails, no slurs, no special "effects" unless they ask you to. Remember: this is bluegrass, not blues! If the saxophone player and the trumpet player can hit their notes spot on, why can't we? Based on my research, I would think that it is also somewhat permissible if we have to change harps — after all, before the valves are invented, horn players had to swap their instruments around for different keys.

While it is possible to play it with overbend (or XB-40), the fact is that bending/overbend is hard to be played spot on. It is much better to play it with a chromatic harmonica. If you will, treat it like playing classical music.

Blues, Rock, and Country
Typically, you will play the blues with the following: And of course, the harmonica, which provide much of the melody, based upon the chord progression. Sometimes, however, the harp may be used to play chord accompaniment.
 * Vocal (main melody)
 * a bass, for bass accompaniment
 * a percussion (be it a drum set or washboard), for rhythm
 * a guitar, mainly for chord accompaniment, but sometimes melody

There's a common myth that you must use the diatonic harmonica and play in second position, while chromatic is only used occasionally, for third position. However, this is not true: the truth is that you would rely on bending notes a lot more, and it's a fact that diatonic offer more dynamics during its bend on draw notes. Chromatic harmonica, however, can bend down halftone in both blow and draw, and thus can actually be suitable for any blue songs — if you can make it sound good in that piece of music.

(As for those that want to point out a certain so-called "blues tradition", this is no different from classical playing that requires certain "such and such". No?)

Still, the need for chords may push people to play in position only. The keys that are most likely occur vary from different researches, but in general, Blues music require one to have the following keys:

Of course, it is quite common for people not to buy all these harps, either due to expense or wanting to try out a few first before venturing out. While there are numerous studies by famous players, what constitutes as "essential" keys are still questionable.

One school believes the essentials are harp in the key of A, C, D, F (crossharp key: E, G, A, C). C, being the most popular keys of harp available, has many blues song written for it. However, the key of A is also popular, especially since Little Walter used such harp to play his famous instrumental, Juke. On this note, then, Harp in D is also popular to play songs in A Blues scale. finally, Harp in F is used to play C Blues scale. All these are also common in Rock and country music.

That just leaves the harp in the key of G, Bb and E, which provide crossharp key of D, F and B. Of course, by no means are they not important, it's just that (statistically speaking) they are less used. Some researchers claim that Harp in Bb is used a lot in Blues, since it matches the horn and sax well. Some say otherwise, believing Harp in G is even more popular and is essential, while F is used less.

Another school, such as those promoted by David Barret, believe the most important keys are G, A, Bb, C, D. (crossharp key: D, E, F, G, A)

Optimally, to play on all keys, one should purchase all 12 keys harmonica, plus chromatic harmonica for third position and some songs that switch keys a lot, but these seven are the recommended ones.

Also, if using Melody Maker, you only have 5 keys available: A, C, D, E, G (Crossharp key). They are also to be played mainly in crossharp only. Though Lee Oskar's website stated that they are not for blues, during one of his workshops he did use one for a blues jam session.

Since you would use more than one blues harp in a single gig, you should also keep yourself organized:
 * Label the key of the harp so that you can see it in dim light. Most clubs are quite dark, and there's nothing more embarrassing then picking a wrong harp due to inability to distinguish the harmonica.
 * Organize the harp in a clear, concise method — usually by listing them "alphabetically", from the lowest pitch to the highest pitch.
 * A harmonica belt, such as the one made by Hohner, is quite handy, as the harps can be readily swapped out. The one made by Hohner also has the advantage of being able to chain them up to carry all 12 keys around.

Folk, Celtic, and Old-time
Unlike blues, playing Folk, Celtic and Old-Time music on harp is primarily played using first position. However, this does not mean you cannot use a Melody Maker or even a crossharp as long as one uses little or no bending.

Instruments involved are usually of following:
 * Fiddle
 * Flute and tin whistle
 * Bodhrán (percussion)
 * Mandolin
 * Banjo

Other instruments that may be included, but no means necessary, are: What instruments may actually be played during one gig, however, vary.
 * Harp (the string kind)
 * Accordion and Concertina
 * Uilleann pipes
 * Bouzouki
 * Harmonica
 * Guitar

Since a majority of Celtic music is in the key of D and G, while many Folk songs are in the key of C and A, the keys needed are, of course, G, A, C and D. The role will be to play the main melody.

Also, note that it is very common for harmonica not to be welcomed in a band, especially in jazz and bluegrass and classical music.

Of course, one should not let these guidelines limit them. There are players who solely play on chromatic or tremolo and there are those who use overblows for all songs. (Except classical; no debate there, even if it's an amateur playing)