I was suprised to know that the harmonica's great grandpa was from South-East Asia (Indo-China) since the 12th century, and came to Europe. Well since then, that big old bamboo horn developed...
I'm a big fan of Blues music, so there wasn't a doubt that I was interested right away by the sound of the harmonica, from the songs of BB King, Elvis Presley,The Beatles, Bob Dylan... yes sir! On my opinion, no harmonica sounds better than a blues diatonic from the club bars of the American streets or from desert of Western cowboys...
If you want to buy a harmonica to play the blues, make sure you didn't buy the wrong harmonica, the diatonic harmonic sounds way driffrent from the others. There are many kind of harmonica, I'm going to show you a few popular kind that new players may mistake it with the diatonic.
-The tremolo: This one has light kind of sound which is aproppriate with modern love songs and maybe asian romantic love song, so this harmonica is very popular in asian's intrument store, in other word, It'll be difficult to find a Diatonic in asia, you might get a Tremolo instead.
a tremolo harmonica
The tremolo Diatonic has 3 sizes, the 16 holes, 20 holes and the 24 holes. The Tremolo has double reed-plate (the metal plate that make notes when you blow) so if there is 16 columns, there are 32 holes since there are 2 rows.
The tremolo harmonica sounds the same when you blow or draw it, and you can't do anything but blow or draw it, and the tremolo is just for playing melody parts of the songs, not for playing chord or solo, so it's pretty boring.
-The Chromatic. Now I don't know much about this guy but I'm pretty sure it's just for playing simple melody too. This one has much more convenient to play because it has (almost?) every note, there's a button (or something like that) on the side of the harmonica, normally there are major notes when you blow or draw the holes, but if you adjust the button, each note will become its sharp note. There not much you can do more with the chromatic than the tremolo wich is usually cheaper, this one is usually for children to play as I knew.
a chromatic harmonica
-Others like the orchestral harmonica, chord harmonica and some Chinese harmonicas do pretty much the same, but they have certain different sound wich could be interesting. There are kinds that design for playing chords too
a chord harmonica
this Chord Harmonica can play very much every kind of chords:minor, major, sharp, flat, even seventh...
But yeah! nothing interests me more than the diatonic. The Diatonic harmonic is more difficult to play well with tecniques and missing note that you have to figuer out to make a good solo. Each Diatonic harmonica only designed for a few among of chords, like the C harmonica can solo at the C, G, D(maybe) major chord,the diatonic harmonica is just for blues or rock n roll music so it plays very well on seventh chord and rarely on minor chords. With a diatonic harmonica, you can think of your own harmonica solo quickly with the right song,right chords, using various techniques like bending notes, wah wah, the train... everthing that fits the rythm and the chord.
So have a harmonica (10$ or 20$) and have a great time, you can perform with other intruments (usually guitar) by using the harmonica holder. so you can play the guitar for the chord, sing for the melody and play the harmonica for the solo, the chicks are gonna like it XD
I can play the harmonica, not so good but I know a few poppular techniques that I will show you in the note of the near future.
Here are some examples for songs wich has harmonica playing:
P.S: Sorry for the terrible grammar.