Creating a Theme Code
Every tune in the A-Z Listing of the Index has a Theme Code. The reasons for providing these are (1) To find the title(s) of a tune of which the title is unknown or temporarily forgotten (2) To indicate from the A-Z listing the different versions of the same tune that have been published over the years (3) To view a list of titles which have been given to the same tune over the years, often found in cases where vocal first-line titles have overtaken the original titles. Of course there are problems and queries in some cases, but the majority of the tunes are quite easy to encode.
If you have a suitable copy of the music, the code numbers for a tune can be pencilled in directly above or below the beat notes. If no music is available, scribble down the first two bars for 4/4, 2/2, the first four bars for 6/8 and so on (see below), establish the Key Note, and add the beat notes to complete the code. You can then search the Index to identify the tune.
The Theme Code Index is read as a numerical progression, like ABC but in the numbers 1-7 (an octave) ascending. A rest occurring on a beat note appears as 0; accidentals and the Minor Mode are identified by the symbols (sharp/flat) and (sharp) respectively (see below). The octaves below and above middle C are identified by a letter: L for the octave below middle C; H for the octave above and T for two octaves above. The first tune in the Index has the lowest four-beat code 1L1L1L1L; moving up in very small stages, passing 3131H, 5511, 1H31H5, and finishing (about 15000 codes later !) at the highest: 1T1T3T1T. Each is divided into two blocks of numbers: Code A and Code B which consist of four numbers, or three, depending on the Time Signature (see examples below). Code B is usually very different in construction from Code A; together they identify the tune. The Theme Code may also identify groups of tunes that have the same structure (ie: the same beat notes) but may be either different tunes, or versions of the same tune with different titles. In such cases, the only way to be sure is to compare the tunes in question.
To create a Theme Code, study the first few bars of a tune, or jot down the notes on a blank stave. Set down the Time Signature (4/4, 2/4, 6/8 etc.) and establish the Key Note, which is always represented by the figure “1”; no matter what key the music is set in. The Key Note is that on which the melody ends naturally and this can usually be confirmed by a chord. In most written music this can be done even more simply by checking the Key Signature against the last note of the music, for example:
Key of A Major (three sharps): Last note A Key Note A
Key of C Major A Minor (no sharps): Last note C Key Note C; Last note A, Key Note A; and so on.
The Code uses ONLY THE NOTES THAT FALL ON A BEAT. Any beat note longer than a crotchet, eg: a dotted crotchet or a minim, repeats the number (see examples below). The number of beats in a bar may vary (as between 4/4 and 3/4) but the Code is invariably in two groups: CODE A and CODE B.
CODES GROUPED IN FOURS
4/4 time (4 beats in the bar): use the first two bars of the tune; 2/2 (4 beats), treat as 4/4
2/4 time (2 beats): use the first four bars of the tune; 6/8 (2 beats): use the first four bars
12/8 time (4 beats): use the first two bars
CODES GROUPED IN THREES
3/4 time (3 beats to the bar): use the first two bars of the tune
9/8 time (3 beats): use the first two bars
3/8 time (effectively one beat): use the first six bars
6/4 time (double 3/4 time): use the first bar only to make two groups of three