What does "diatonic" mean?

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What does "diatonic" mean?

Postby Bob Lewis » Tue Oct 30, 2007 7:25 pm

Q. What does "diatonic" mean?

A. In modern usage, the word "diatonic" is associated with a 7 note do-re-mi-fa-sol-la-ti scale. The piano provides an excellent metaphor to understand the basic concept. Within each octave, for example from one C note to the next, there are 12 scale steps defining the "chromatic" scale. The white keys are "naturals" and the black keys serve as either sharps or flats depending upon the key being played. The diatonic scale for the key of C would be the seven white keys. The diatonic scale for B would be all the black keys plus B and E. Note that this scale contains a half step between mi-fa and ti-do. All other intervals are whole steps. This corresponds to the piano octave where playing two white keys with one black in between is a whole step. Playing two white keys that are side-by-side is a half step.

A2. 4/1/08
A standard chromatic has 12 notes in an octave. An autoharp has 3+ octaves. A real diatonic has 7 notes in an octave, just do-re-mi-fa-sol-la-ti. There are configurations for every possibility between 7 and 12 notes. The most popular GDA has 9 notes. The point is that when not needing 12, the extra strings are tuned the same as a neighboring string, creating "doubled strings". That, plus the fact that more strings are now open on each chord, gives a "diatonic" a bigger sound with less of a scratch effect, the "scratch" coming from strings damped by felt, those strings which don't belong to a chord.

The "3-key" instrument is important in that it provides some of the benefits of a chromatic while having enough strings open on each chord to take away that washboard scratch that one gets on a fully chromatic instrument. A "3-key" is not diatonic per se, but if fitted with "lockbars" that hold out notes that don't belong to one key, it can be played using open notes, as if a single key instrument. Without using lockbars, many chromatic tunes, those using more than a single diatonic scale but not a full 12 tones, can be handily played, no different than a fully chromatic instrument.

So a 3-key, typically GDA, may be referred to as a "diatonic" but technically it is not diatonic. The term "diatonic" has come to mean "not chromatic". I suppose we could say contra-chromatic, but based on precedent that term suggests a very large autoharp. That leaves us understanding that the term diatonic is abused, and one could easily become confused about what the term means.

When an autoharp has less than 12 notes, one may need fewer than 21 chord bars. There are more than 21 chord possibilities on a chromatic, but that is all that will fit on the instrument, one reason why it cannot play in all keys or at least do it well.

A diatonic can have the same chords but fewer of them. The tuning of fewer than 12 notes per octave won't support as many scales.

Aside from "what does diatonic mean?", one might ask "why do people want a diatonic?". The primary answer is that it sounds better. The original autoharp was single key C. It has been altered to make it more versatile, but the sound then becomes compromised, difficult or impossible to be optimal. About the closest you will find is among the most particular pros who use single key instruments with very few chord bars. Those among others include Bryan Bowers in the US and Mike Fenton in England.

Those who choose the 2 or 3 key still have the same answer. "It sounds better" and provides a more pleasing experience. What it can't do is play all tunes, those that range so far in what chords are needed. One would either need to maintain a chromatic autoharp (own more than one autoharp) or forgo being able to play tunes that require more notes and chords.
Bob Lewis
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