The chordPro file format has been around for decades.  It purpose is to represent a song with chords in an easy-to-parse format.  It can be as simple as:

{title:Wonderful Time} {subtitle:Words and Music (C) 2007 Adam Monsen} [C]Every[G]body, [F]let's have a wonderful time,

Through the years many programs were designed to perform one task or another; while most supported on visualization and printing, some included advanced features such as chord transposition.  Whichever the focus, editing, creating or mantaining song files, many additions were made to the original standard through the years.

Some of these additions made it in more than one software, others were adopted or invented by mainstream applications and became de-facto standards.

In this table we tried to bring together a near-complete list of commands along with references to the sources, which were both details of software products and more general discussions.