update piano readme

piano/README.md

@@ -49,7 +49,7 @@ For example, the data for the 2nd take with metronome, at normal speed and exagg
 
 <a name="take-data"></a>
 ### Take data
-The following data is available for every take:
+The following data is available and aligned for every take:
 
 - __Audio__
  `audio.wav`
@@ -58,6 +58,7 @@ The following data is available for every take:
 - __MIDI__
  `score.mid`
 - __Motion Capture__
+`mocap.csv`
  Position and orientation of 22 body limbs. Due to occlusions, the position of body limbs below the abdomen is unstable.