A Player's Guide to Chords and Harmony by Jim Aikin

sense if the chord were referred to as an A rather than a C chord. In any case, the chord's ambiguity renders this distinction pretty much irrelevant.
    Because each diminished 7th chord is in reality four different diminished 7th chords, there are only three distinct diminished 7th chords in the chromatic scale. To give them their convenient (rather than academically correct) spellings, the three chords are A-C-E6-F#, B6-C#-E-G, and B-D-F-A6 (see Figure 5-3).

    Figure 5-3. Because the diminished 7th chord is symmetrical with respect to the 12-tone equal-tempered scale, the scale contains only three different diminished 7th chords, which are shown here. Any of the four notes in one of these chords can function as its root. While there's a correct way to choose enharmonic spellings for the notes, in practice most arrangers choose a spelling that's easy to read.
    Augmented-Major 7th & Minor-Major 7th. The last two 7th chords are used less often than the first five, but they provide distinctive harmonic colors that are worth knowing about. The augmented-major 7th, shown in 5-2a, gets its name from the fact that it includes an augmented triad and a major 7th. The minormajor 7th (Figure 5-2d) gets its name from the minor triad and major 7th. In both cases, the name mentions the type of triad first, and then the type of 7th.
    For review, let's look at the chords in Figure 5-2 again (see Figure 5-4), this time with their names. The major-key diatonic 7th chords are identified in Figure 5-5.
    The Colors of the 7th Chords. It's difficult or impossible to fully explain the meaning of any type of music or musical phenomenon in words. If it were easy, we wouldn't need music! Nevertheless, as we get deeper into harmony, it becomes clear that the chords we're exploring have emotional connotations. That's what makes them useful.

    Figure 5-4. The chords in Figure 5-2 have names, which are shown here. As usual, all of the chords are shown with a C root, purely for convenience. You should try transposing these chords to the other 11 roots in the scale to get a feel for how they appear on the keyboard.
    Without wishing to restrict your own usage of these chords or the meaning you find in them, which may be different from anything other musicians have ever envisioned, we can make a couple of basic observations. Most listeners feel that the major 7th chord has a pleasant, settled, happy sound. The minor 7th, in contrast, is more sad and thoughtful. The dominant 7th is bold and purposeful. The major-augmented and minor-major 7ths are edgy and unsettled; because of their instability, they're used most often as transitional chords. The half-diminished 7th is also a transitional chord, but its sound is warmer. The diminished 7th chord is ambiguous and therefore very unstable. It always serves as a lead-in to some other, more stable chord.

    Figure 5-5. The diatonic 7th chords in the major scale.
     

CHORD SYMBOL ABBREVIATIONS
    Having to write out the full name of a chord type in sheet music each time the chord is employed would make for a messy, hard-to-read page. Musicians have come up with concise abbreviations for many commonly used chord types - not just 7th chords, but other types, as explained in later chapters. While there is not complete agreement among musicians about which abbreviations should be used to indicate which chords, only a few systems (which are similar to one another except for details) are in common use. These symbols are very commonly employed in lead sheets. In fact, we've already seen a few of them in Chapter Three.

    The general rules that are employed for generating basic chord symbols are as follows:
    1. The root of the chord is indicated by its letter name (almost always shown as a capital letter). Any chord whose root is C will have an abbreviation that begins with the letter C. If necessary, an accidental will be part of the root name. A chord whose root is F#, for instance, will have an abbreviation that begins with