Playing octaves on the chromatic can be difficult at first because the notes are four holes apart. This means you have to block the holes in between with your tongue. The following example is a demonstration of several pairs of octaves on the chromatic harmonica. Practice the technique using exhale and inhale notes in one position before trying the whole exercise. It is difficult so be patient and practice it for a short time each day among your other exercises. Once you can do the basic exercise, try playing some scales in octaves as demonstrated in example 39.
The next step is to play some melodies in octaves as shown here. There are no breathing indications under the notes here, but you already know all the notes so this shouldn’t be a problem.
This one is a Blues in the key of D minor. To hear great examples of playing octaves on the chromatic harp, listen to Blues players like Little Walter, James Cotton and George "Harmonica" Smith. Be patient with this technique as it takes quite some time to master.