To find the most suitable harmonica for playing a song, enter the chords (major, minor, dominant seventh, augmented or diminished chords) that are played in the song and press Calculator. To find the most suitable harmonica for playing a particular melody, enter in the row below how many times each note is played in the melody and press Calculator. You can also mix melody and chord information. To start over with a new song, press Reset. 
Of course, this is just a tool; in the end, your ears will have to decide which one you like best!