Mode Key & Scale

The terms Mode, Scale and Key are given different definitions by different sources.  In Zylaphon these terms are defined as follows:

Mode

A Mode is a sequence of intervals defined over a tone class set. The chromatic-diatonic twelve tone octave sequence of common practice is the most familiar tone class set. For an example consider the Ionian (major) mode which is defined by the following pattern of intervals which ascends in pitch from left to right: 

                                                                                                                                                        Half Step,

                                                                                                                                  Whole Step,

                                                                                                             Whole Step,

                                                                                        Whole Step,

                                                                        Half Step

                                                    Whole Step,

                                Whole Step

Key

If we assign to a Mode the name of the first tone in its first interval we have defined a Key. For example, A Major, here below directly derived from the interval pattern above by starting with A

A,   B,   #C,   D,   E,   #F,   #G,   A

i     ii     iii    iv    v     vi    vii    i    (The Key object also associates scale degrees with the tone names.)  

Scale (member of Key)

A scale is a pitch referenced expression of a key,  for example the major scale beginning on A midi 57 (A 220)

In Zylaphon the scale object acts like an array of consecutive Pitches that cover the MIDI range of its Key.  Elements may be accessed either by scale degree and octave or by MIDI index.

Tonal Scope 

The chromatic-diatonic twelve tone octave sequence tone class set (think piano keyboard) has countless significant variants when tunings and sub sets are included. Thus the number of possible distinct pitch class sets and modes that can be defined over that set is quite large.  It covers the vast majority of western music composition. As planed Zylaphon will implement only this tone class set (and infrastructure its aforementioned pitch class set variants) during its initial phase.  In its second phase it would be very desirable to implement at least one additional staff-note-accidental notation system capable of effectively notating scales defined over more than 12 pitch classes, such as W. Carlos' 17 "tone scales".

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