Performance qualities are decisions that are taken by the performer. Such decisions are influenced by the qualities of a particular instrument and the characteristics of the person playing it, along with several other factors.
For example, the decision to play portato (unconnected / non-legato) is not related to the qualities of the instrument at all, as every instrument is able to play short notes. While in Baroque music, quarter notes tend to be played portato (shorter with more space between them). In this example, the decision was taken based on music style only, rather than taking instrument qualities into consideration as well.
Here is another example of a decision taken by a performer, but this time it is directly related to instrument qualities. Look at the following cello part. The performer must decide how to play the “A” note, knowing that it can be played either on the open A string, or on the D string using their finger.
Playing it on A string breaks the homogeneity of the phrase. This explains why, in this case, most players choose to play the “A” note in on the D string.
In order to ensure that our system is as human as possible, our Performance Quality Model considers hundreds of cases, and is able to make the same intuitive decisions that experienced musicians would choose.