The secret message by the Princess is in her Maid's room (first floor of the castle).
The secret note is in the unreachable Princess tower. To get it :
Get the rope from the mill (by the mud) Tie...
If the time is 4/4, the following notes would be: A quarter note (1/4 or 2/8) of the measure) A half note (2/4 or 4/8) of the measure 2 eighth notes (2/8) of the measure.