Walk into a music store and you'll see a few different types of harmonicas. The most common are chromatic, tremolo, and diatonic. For blues, folk, and rock music, the one you want is the 10-hole diatonic harmonica. It's the classic sound you probably have in your head.

Diatonic harmonicas are tuned to a specific key, like C, G, or A. A great first harmonica is one in the key of C. It's the most common key, and many beginner lessons and songs use it. Look for a reputable brand; a well-made instrument is easier to play and sounds much better.

How you hold the harmonica affects your tone. The goal is to create a resonant chamber with your hands. Most players hold the harmonica in their left hand, between the thumb and index finger. The numbers on the harmonica should be facing you.

Cup your left hand around the back of the instrument. Then, bring your right hand over your left, creating a tight seal. You can open and close your right hand to create a “wah-wah” effect.

Breathing is the most important part. Don't think of it as blowing; think of it as breathing through the harmonica. Your breath should come from your diaphragm, deep in your belly, not from puffing your cheeks. Inhale (draw) and exhale (blow) gently and steadily. Relax your jaw and throat to let the air flow freely.

A standard 10-hole diatonic harmonica uses something called the Richter tuning system. This layout is designed to make playing chords simple and intuitive. Each of the ten holes produces two notes: one when you blow out, and another when you draw in.

Look at the blow notes. In holes 1-2-3, you have C-E-G, which is a C major chord—the home chord of the key. Now look at the draw notes. In holes 1-2-3-4, you get D-G-B-D, which forms a G major chord, another essential chord in the key of C. This layout makes it easy to play simple chord accompaniments for folk and blues songs.

Because diatonic harmonicas are locked into one key, you'll eventually need a few of them to play along with different songs. If a song is in the key of G, you'll need a G harmonica to play along with it. This is called playing in 1st position, or "straight harp."

However, for blues, players often use a different technique called 2nd position, or "cross harp." This is what creates that classic, soulful blues sound. To play cross harp, you use a harmonica that's tuned a fourth higher than the song's key. For example, to play blues in the key of G, you would use a C harmonica.

For now, don't worry too much about all the different positions. Just know that your C harmonica is perfect for playing songs in the key of C (1st position) and for playing blues in the key of G (2nd position). It’s a very versatile starting point.

With these basics, you have a solid foundation to start exploring the harmonica.