structural:summarization
Diatonic

Strictly speaking, diatonic denotes any harmonica designed to play in a single key—though the standard Richter-tuned diatonic harmonica can play other keys by forcing its reeds to play tones that are not part of its basic scale. Depending on the country, "diatonic harmonica" may mean either the tremolo harmonica (in East Asia) or blues harp (in Europe and North America). Other diatonic harmonicas include octave harmonicas.

Here is the note layout for a standard diatonic in the key of G major:

Each hole is the same interval (here, a perfect fifth) from its key of C counterpart; on the diatonic scale, a G is a perfect fifth from C. The interval between keys can be used to find the note layout of any standard diatonic.