The changes of a "popular song" standard can be divided into blocks, where each block represents a (more or less) commonly used chord sequence. These blocks can be seen as "functional" in that they often have a purpose, or function, such as modulating to or from a different key. The piece can then be memorised and recalled by the blocks rather than the individual chords.
This has two advantages:In this continuing project, the chords of various jazz standards are presented in a parallel text, as changes, and as functional blocks.
The charts of the pieces are described in HTML, which provides a means of defining the appearance of the chart and also allows fast cross referencing. Each functional block in the chart is linked to its explanation, and that in turn links back to every piece that uses it.
The translation of these standards into functional blocks is a test of the generality of the system, both as a theoretical idea and in terms of the representation used here. Ideally the number of different functional blocks should be kept as small as possible while being applicable in as many standards as possible, but still providing enough discrimination where differences exist. When a standard is added to the database, it may be necessary to create a new block where a suitable one doesn't exist, or it may be possible to alter the definition of an existing block to improve its generality.
In some cases there may be a hierarchy of functional blocks, where blocks that can occur on their own also have a frequent use in a particular sequence. In this case it has been decided to put the top hierarchical layer on the sheet, and expose the lower layers when the reference is followed.
The changes are described in relation to the key of the piece, using a Roman numeral system which needs some explanation. The changes are not necessarily based on any particular version of the piece, either performed or written, but may be honed down to the basics to make the functional structure clearer. In some cases, alternative changes may be referred to, and sources referenced.