Solo tuning

Solo tuning is a system of choosing the reeds for a diatonic wind instrument to fit a pattern where blow notes repeat a sequence of
and draw notes follow a repeating sequence of
. Or, alternately, these blow notes and draw notes, raised by a semitone, to
and to
Traditionally, this tuning is used with chromatic harmonicas, as opposed to the more common and popular diatonic harmonicas, which use Richter tuning.
The first diagram below shows that solo tuning includes all the major scale notes for all three octaves, while Richter tuning has some missing notes such as A and F on the lowest octave. In order to include the four notes D F A B on the draw holes, solo tuning uses four holes for each octave, resulting in pairs adjacent of C notes on the blow holes, unlike Richter tuning.
For example:
and