When performing any type of music, the performer is expressing the "character" in their own way. They add emotions and different, unique characteristics to the character that is being presented through the music that the composer wanted portrayed when performed. Therefore yes, when performing music or theatre, it is very artistic.
While music composition may be the initial artistic impulsion behind the creation of an artistic object, it cannot be realized and transformed into an artistic experience without the performer. This realization requires both intuition and an enormous number of artistic decisions on the part of the performer. As a composer, I have worked with literally hundreds of professional classical musicians over the years. Each has their own unique artistic contributions that they have made to any project or performance; they are collaborators and equal partners in the creative process (from my point of view). A performer's artistry determines whether a composition shine, or fail; whether a great piece flops or a mediocre piece soars.
Just listen to two different performers playing the same work. Their performances will almost certainly be very different. Each one will bring out different nuances, add their own personal touch, interpret the composer's intentions slightly differently, etc.
A "non-artistic" performance of a work, such as that made by a computer, will often sound artificial.
Firstly, sorry about the clumsy title. I was evading the filter again.
I was inspired to make this poll after a user on DDO commented that memorising a song isn't enough to be qualified as art. Performing music is highly artistic. When you sing a song or play a piece on an instrument, it isn't just about getting all the notes right. It's about getting the mood of the song, bringing out the nuances, and so on. It's about trying to get the intentions of the composer and displaying these intentions in your playing.
Let's say you're practising a piece of music, and you see an interesting harmony there. It's dissonant. Why did the composer do this? Did he or she intend tension? If so, how should you play the note to bring out this tension? All of this is highly artistic, and thus music performance should be considered art.