This is that riff that blues singers use.
You sing something then play it. (many times)
you can play it on almost any 2 strings, or play it
in power chords. I think it sounds the best this way.
|-----------|
|-----------|
|----2-0----|
|--2-----2--|
|-----------|
|-----------|
Here's a way to play it on a C harmonica.
s - suck
b - blow
5b 6s 6b 5b
That's all folks!
have fun!