Strange rhythm is estimated as an error (frame 250-280)

In this example, there are 2 labelled portions very shortly spaced. This is a sensible annotation because they seem as two separate mistakes. However, it is worth highlighting that this is not always the case, and sometimes it is not clear when an error starts and ends. 

All models (except AE) predicted two separately labelled regions.

Around frame 150 - as a flipside of detecting erroneous pauses in music performance, the system sometimes mistakes notated musical pauses as errors.  

Around frame 1700 - the right hand contains three repetitions of a motif (ascending thirds).   Some trained models consider this as an error, presumably since a common error mode in beginning pianist is to pause and repeat parts where a mistake has been made.   Humans presumably disambiguate repetition as a result of composition versus errorneous performance by looking at a longer musical context and metric structure. 

Around error 120-200 - a climactic held chord is detected as an error, presumably because a novice pianist has a tendency to hold the pressed keys when sightreading. 

Around frame 2300 - This piece contains graceful ornaments (appoggiatura), which is often mistaken as errors.  This happens presumably because hitting adjacent keys is a common error mode, so it is difficult to disambiguate between intentional hitting of the adjacent keys (ornaments) versus mistakes.