Chord-finder slide-rule

Roger Sapolsky

I personally do a lot of chord programming on my AMPLE System. For this purpose I have used in the past a BASIC program running in a small SHARP computer which displays the component note names of a chord of a given type. I later adopted a simple device faster in operation, let's call it a 'chord-finder slide-rule'. More about this later.

Before going any further, I will briefly describe the syntax used to define chords in sheet-music parts. All 'symbols' begin with a capital letter, the chord Base note, which can be followed by a sharp/flat. If nothing (or 'maj') follows, the chord is major. If 'min' or 'm' follows the chord is minor. Other alternatives are:

'7', '9', '11', '13' -> dominant 7th to 13th

'dim' or 'o' -> diminished (7th)

'aug', '5+' or '+' -> augmented (5th)

'min7', 'm7' or '-7' -> minor 7th

Take the example of a C7 chord. It includes the tonic C, the major 3rd E the perfect 5th G and the minor 7th Bb. If the 5th is lowered a 1/2 tone, the symbol becomes C7-5 or C7b5. The altered interval is here indicated in the symbol.

A variety of chords may be created from 'normal' chords by altering one or several of their component notes. It would be pointless to list them all. C7b5#9 or b5+9 or -5/+9 has an augmented 9th added. Symbols such as Eb7/4 (sus4) or Gm6/9 simply indicate that a 4th must be added to the Eb7th chord, and a 9th to the Gm6th chord. Double symbols such as Db/G apply to 2 different chords played simultaneously. The chord-finder will demonstrate that Db+G = G7-9+11. Strange arithmetic!

The chord-finder is shown on the sheet that accompanies this disc. It is self-explanatory.

Even if you don't have a great academic musical knowledge (which I don't), it will give you, at a glance, the composition of any chord, whatever its complexity.

Much of the colour and originality of a piece of music will be lost, should the chords be 'simplified'. Perhaps some members will question the need to know all of the 6 notes included in a 13th chord, for instance, since the AMPLE system seldom has 6 voices to offer us for accompaniment. In fact, the notes of a chord have an unequal importance, some are essential, others not.

The following notes will help the user make a selection.

The 3rd must be kept in all types of chords, because it makes them major or minor. In a dom7, use at least 3 and -7 (minor 7th). Add T and 5 in order of importance. In chords such as 7, 9, 11 and 13 ('Dom' and the ordinals are implicit) the intervals included in the symbol must be used. For example, a chord including 3, -7 and 13 is a 13th (without T, 5, 9).

Obviously, the altered intervals in a chord give it its special flavour - they mustn't be dropped. Thus, while a 7 doesn't suffer too much from the loss of its 5, a 7-5 , or a 7+5 is inseparable from its altered 5th.

Since 'dim' and 'aug' have equal intervals (1½ and 2 tones respectively), all of their notes have an equal importance. It may be of interest to say that dim chords played at 1½ tone intervals do not change their name. Try the well-known effect: Cdim 3@Cdim 6@Cdim etc. (4@ 8@ etc. with Caug). 'C' is just an example.

On the slide-rule itself, several of the listed chords have their 'important' notes underlined, as a reminder of what has been explained here.

Chord symbols read in sheet music parts, and words to define them in AMPLE programs can be made identical, with 2 exceptions:

1) Use a lower-case letter to begin the word.

2) Don't use standard note names for your chord word. Calling your chord word, for example, 'g' will just cause confusion. Using 'gk' or 'gz' will identify the chord you have defined. In case of a Gflat chord, name it 'g-', not ‘gb’ of course.

Using this method allows easy comparison with sheet music when debugging. Also, the contents of a chord word should be apparent from its name.

Octave settings included in words will obviate the need to keep track of the successive chords' first notes.

The transposition word '@' is also a boon when creating new chords from existing words, provided the preceding number is small enough to locate the new chord in a register not too distant its neighbour's, though a shift of register is often acceptable.

Two further possible applications of the chord-finder:

1) It makes the composition of a counter melody easier. Here is one bar taken from a solo played in Dmin, the underlying chord being A7 (A+CEG). It goes like this:

+CEG-B+CEGf

It is clear that 6 out of 8 are notes of the A7 chord. Hence the counter melody can go like this:

a+CE/A+CE/

To avoid going into details, I suggest that you experiment and trust your ears to find suitable matches for Bb and f. I suggest G and d. The pair 'fd', by the way, belongs to the Dmin chord related to A7 and is used often in neighbouring bars. No wonder f and d go well together.

2) Along the same lines, elementary bass part composition is also made simpler, using segments of known arpeggios arranged with discretion on the bass clef stave. The result, always acceptable can later be improved by adding passage notes, accents, by varying the number and duration of notes taken from each arpeggio (2, 3 or 4 different chords may be used in a bar), etc..

The chord-finder won't, unfortunately, do the programming for you. However, your manually programmed chords may have greater variations and subtleties than have those yielded by a computer. In slow tempo jazz ballads, this may be particularly appreciated, when compared with monotonous chord patterns.

A few tips concerning chord programming.

'Closed' chords played on the lower part of the register sound fuzzy when Upright is being used. For example, a chord such as

-1: c(EGC)

should be avoided. Spacing out its three upper notes, for example,

-1: c(GEC)

makes it acceptable. For some mysterious reason, -1:C(EGC) sounds 'lower' than c(GEC)!

The Upright instrument loses much of its realism when playing low pitch notes; say, lower than -1:C. Using an alternative instrument for the voice in charge of low notes brings a marked improvement.

Starting from the definition of 'Upright' enter

1 CHAN 192 SHIFT

below 2 CHANS, then change 200 OFFSET to 110 OFFSET. Leave other values the same. This instrument will sound good in the pitch range -3: to 2:.

Having a different player in charge of the 'low' note rather than having 4-note chords played by one player will make rhythmic or harmonic effects easier to program. For example, when a note needs to be sustained during a progression of chords.

For those who wish to experiment, I have listed 2 sets of chords for the accompaniment of a 12-bar Bb blues.

1) 'Traditional':

Bb | Eb7 | Bb | Bb7

Eb | / | Bb | /

F7 | / | Bb | Eb7 F7

2) 'Be Bop':

Bb | Eb7 | Bb | Bb7

Eb | Bbdim | Bb Cm7 | Dm7 Dbm7

Cm7 | F7 | Bb | Eb7 F7

Note: If different chords played in succession have one or more identical notes, these notes should be similarly located on the stave. The dissimilar notes should go to the nearest suitable locations. For example, when

"b-" [-1: -b(DF-B)]

is followed by

"E-7" [-1: -b(-D-EG)]

the note '-b' doesn't move.

The purpose of this is to obtain a smooth progression without large displacements in registers.

'Bass' notes followed by chords played in a medium register sound better than a monotonous guitar-like strumming of chords.

This example (two bars of the Bb blues) uses alternating bass notes and chords:

48, 2: '-b !F(-BD)

'!f(^^) !F(-BD)

'!-e(^^) !G(-B-D-E)

'!b(^^^) !G(-B-D-E)

0,^;

The low pitch note is often the tonic with the 10th added, for example, -b(!D).

A copy of Roger Sapolsky's chord-finder slide rule is included with this disc.