notes on music data

Song
* Title (string)
* Artist (string)
* Album (string)
* Albumart (string; uri to picture)
* URI (string; uri to song)
* Duration (float; seconds)
* Encoding
  - Codec (string; MP3; M4A etc.)
  - SampleRate (float; Khz)
  - BitDepth (int; number of bits per sample)
  - Channels (string; number of channels in track e.g. 1, 2, 5, 5+1, 7+2)

Play List
* Songs (array of Song)
* Length (float; seconds)

PlayerState
* Status (string enum: Play, Pause, Stop, Starting, Ending)
* Playing (Song)
*