The following music sheet:

means that:

1. at the very beginning of the song, that is at \( t=0s \), a pianist must press the la key.
2. at \( t=0.6s \), he must release the la key and immediately press it again
3. at \( t=1.2s \), he must release the la key.

Releasing a key and pressing it again at the exact same time is something that is literraly impossible to do for a human being. However, for a computer this lead to the situation where a sound is emitted but it doesn't look like the key was pressed again.

Let's look at the following video, and let's pay extra attention to the la key displayed on the keyboard at the bottom. It looks like it is pressed at the beginning and released at the end only, while in the middle of the video we can distinctly hear the la note being played again.

When looking at the keyboard only, it looks like the la key is played once and held as if it was a white note, not a quarter one.

To overcome this issue, the program applies a similar strategies as the one used to fix "overlapping" notes. It will detect when a note is said to be released and pressed at the exact same time, and it will then introduce a small temporal gap. This mimick human's behaviour. The first note will be released slightly earlier. Its duration will be shorter by either 1/4 of its duration, or 75 milli seconds, whichever is smaller. These values where chosen completely arbitrarily though. The result is the following video where one can clearly spot when is second la played only by looking at the keyboard.

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