How to Create a Train Sound With a Harmonica. The harmonica is a little instrument that creates big sounds. Harmonicas are famous for being able to mimic the sound of a train whistle. Although it sounds like a variety of harmonica notes playing at one time, it's really more an exercise in proper breathing.
Place your puckered lips over the 1, 2, 3 and 4 draw and blow holes.
Hit your tongue to the roof of your mouth as you draw and blow to achieve the separation in the sounds. It should feel like a tapping on the roof of your mouth between draws and blows.
Keep your lips loose and flexible as you're doing this exercise. This is true for all harmonica playing, as relaxed lips make the best sounds.
Increase your speed on the draw and blow a little bit at a time until the notes being played slur together.
Pucker your lips a bit more as you continue to play quickly. This will help isolate the notes that you are going to bend to make the train sound.
Push the harmonica up at an angle toward the roof of your mouth as you draw then blow, draw then blow. The train whistle sounds when there is no space between the draw and the blow, so this motion should be smooth.
Use your diaphragm for breathing in and out when playing the harmonica. Expanding the diaphragm lets you draw in more air and have better control as you exhale.