Harmonica/Types of harmonica
There are three basic types of harmonica; chromatic, diatonic, and the Asian tremolo.
Chromatic harmonica 
This type of harmonica can play semi-tones easily. In this book's context, it refers to either the traditional version (using a slide), or the Tombo's slideless versions. Horn harmonica is a different category altogether and, as of now, it will not be covered (since it's only popular in East Asia, and for Orchestra purposes only). In general, materials for chromatic harmonicas is lacking, regardless of location, and as such, it is usually recommended to be played after one has learned the basics of the 10-hole diatonic or Tremolo harmonica. However, if one manages to find good materials, chromatic harmonicas are just as easy to learn.
It has ten holes which offer the player 19 notes (10 holes times a draw and a blow for each hole minus one repeated note) in a three octave range. The standard diatonic harmonica is designed to allow a player to play chords and melody in a single key. Because they are only designed to be played in a single key at a time, diatonic harmonicas are available in all keys.
It is most commonly used in North America and Europe and is a main feature of Blues music.
- Valved Diatonic - one of the most common ways to let a diatonic play chromatic notes is to place windvalves over hole 1-6 draw reeds and hole 7-10 blow reeds. Therefore, one can bend on all blows and on draws to get the chromatic notes.
- Suzuki Overdrive - the Overdrive can be seen as an overblow trainer, in which precisely placed holes on both covers allow the player to stop appropriate reeds, allowing the harmonica player to overblow easily.
- Hohner XB-40 - the XB-40 is basically a combination between a chromatic harmonica and a valved diatonic. It has 40 reeds; 20 of them activate when playing normally, and 20 others operate when bending occurs. The chromatic scale can be achieved by bending.
East Asian Tremolo 
This version of a tremolo harmonica is the standard variant of diatonic harmonicas in East Asia and have more materials. As such, for beginners in East Asia, this type of harmonica is the best.
Other types 
Other types of harmonica are the European Tremolo, the Octave harmonica, the very rare Chord harmonica and the Bass harmonica. These are designed for ensemble playing. A beginner would not need to worry about learning these types of harmonicas just yet.
Playing chromatic note on a harmonica — which is better? 
In general, there are five main ways to get chromatic notes: use a chromatic harmonica, overbend on a diatonic, valve diatonics, use the Hohner XB-40, and using two 24-hole tremolo stacked together. As to which is better, here are the following benefits:
|Octaves||Chords||Rapid key switching||Size||Learning Difficulty||Tonal Precision||Tonal Quality||Playing range||Price|
|Chromatic||All blows and draws||I, ii, vii||Possible||Big||Easy||Spot on for all notes||Quantitized (tonal vary little)||Most common is three octaves; Four octaves is also quite common||Expensive|
|Overbend (diatonic)||All blows, some draws||I,ii,V-7(straight harp)
|Possible||Small||Very difficult to hit the overblow itself (easy if using Suzuki Overdrive), but once the technique is figured out, it's easy to lean onto the note with no more adjustment||Sound different for overbended notes||Very dynamic||Three octaves is very common; Four octaves is available if using a four octave diatonic (which is rare)||Cheap (but need proper calibration)|
|Valved diatonic||All blows, some draws||I,ii,V-7(straight harp)
|Possible||Small||Slightly difficult||Sound "bluesy" for bended notes||Quite dynamic||Three octaves is more common; Four octaves is available if one valved his/her own four octave hamonica (which is rare)||Cheap if valve it yourself; expensive if buying Suzuki MS-350v|
|Hohner XB-40||All blows, some draws||I,ii,V-7(straight harp)
|Possible||Sort of Small||Difficult (Way too easy to bend notes; need precise control in order to get the proper note)||Spot-on for some notes, "bluesy" for others||Most sounds are dyanmic; quantitize for some||Three octaves only||Expensive|
|Stacked tremolo||All blows and draws||I,ii||Not available||Big||Easy||Spot-on||Quantitize||Three octaves only||Relatively cheap|
As a beginner, one does not need to worry about playing chromatic notes just yet. However, if you're seeking more in-depth information on which type of harmonica is the best for performing them, see below.
Due to the table, if one wants an instrument that is capable of thickening the sound and playing many tricks and basically "one-size-fits-all", but incapable of playing chords and performing a "bluesy" wail (a bane of classical music), then a chromatic harmonica, especially a four-octaves version, is the only way to go. This is because the lowest octave actually allows tranposing to lower octaves; additionally it will make the music sound closer to saxophone in lower registers.
However, if one wants to gain that certain feeling in blues and jazz (growling and wailing, for example), it is a good idea to either get the valved harmonica or learn overbends; however, much learning is needed since those methods depend on proper embouchure.
Alternatively, the XB-40 is quite easy to bend, but perhaps too easy to bend; the player needs precise control of the bending in order to only bend a semi-tone down instead of a whole tone down. However, it has the tonal quality and precision of both diatonics and chromatics if the player is trained properly; adding to the fact is that it is capable to do some true tones and double reed bends because of the additional reeds. Thus, it can be very suited for hands-free playing at the very least, and is a definite must for people interested in playing music that have a bluesy or jazzy feeling; lastly, since there are many ways to play the same note, it is easier to play legato on XB-40.
Still, it is not without problems; the C-key model, for example, often warrants complaints about its third octave, in which bending (blow and draw) is difficult to perform. Also, it requires precise tonal control (not unlike playing trumpet), as it is easy to miss the required note during bending and accidentally bend down a whole tone. Lastly, it is limited to three octaves, making it restricting if players truly want to play in numerous keys. (Of course, Toots use a standard 3 octaves harmonica to play jazz, so maybe it's not much of a problem.)
Stacked tremolos, as common as it is in East Asia, just do not cut it, since switching the notes in a key is very slow. If one must have the tremolo sound, get Suzuki's chromatic tremolo, which plays just like a conventional 16-hole chromatic.
All in all, it depends on how a player approaches playing music. Keep in mind that just because a piano is designed to play classical music doesn't mean a jazz player cannot play piano jazz with the proper feeling. Likewise, a chromatic harp can also play jazz harp, as long as the musician is skilled enough. On the other hand, classical music has such a rigid requirement that some view XB-40 as inappropriate; to those classical musicians, they will simply call it "classical music play in jazz style", as they will deem the wailing effect not proper. Others, however, believe that it's fine, so long as the player can hit the notes precisely.
There is a strong incentive among North American players to play chromatic-capable harmonica in positions only, and thus treat it as diatonic. This is inappropriate, as it defeats the purpose of a chromatic-capable harmonica. They should instead train themselves so that they can play with only one or two harmonicas (e.g.: chromatic and XB-40)
|Getting started: Why should I Play Harmonica? | Types of harmonica | Anatomy of a Harmonica | Harmonica Purchasing guide|
|Playing the harmonica: Basic Holding and Playing a Harmonica | Tablature | Basic Chords | Bending|
|Additional techniques: Advance Chords | Advance techniques | Self accompaniment|
|General harmonica theory: Chromatic Harmonica | Positions | Tremelo | Ensemble Playing | Music Style | Learning Songs | Improvising | Recording | Playing with Amp|
|Cleaning and maintainence: Basic Maintainence and Care | Advance Maintainence |Harmonica Modifications |Tuning|
|Appendices: Harmonica Layouts and Alternate Tunings| Harmonica Positions Chart | Blues | Writing Songs|