Melody & Lyrics: Version 1.0
* Melody channel not declared are auto-created.
* It's possible to play 0..* melodies.
* It's possible to assign lyrics to each melody channel played.
* Melody & Lyrics are parts of PlayStatement.
* Can be write in any order.

Play Chords
 
* Can't assign lyrics to a not-playing melody channel.
* Can't assign lurics to an harmony channel.