pianist
The word 'pianista' is a noun in Spanish. It corresponds to the English word 'pianist'. A 'pianista' is a person who plays the piano. In performing genres, a pianist could be an accompanist, improviser, session musician and it is seen as an essential skill in classical music, musical theatre, jazz, blues, and many other music genres.
The pianist is tuning the piano before the concert.
In this sentence the pianist plays an active role, as indicated by the verb 'is tuning'. The verb 'afinar' is an action that only an expert, like a pianist, can do before a concert, specifically talking about tuning a musical instrument, in this case, the piano.
A good pianist has to practise every day.
This sentence emphasizes the importance of daily practice in order to be a good pianist. The verb 'has to' translates to 'tiene que', which is used in Spanish to express necessity or obligation.
My friend is a talented pianist.
The sentence describes a positive quality about a friend, identifying her as a 'talented pianist'. In Spanish, adjectives usually come after the noun they modify, which is why 'talentosa' (talented) comes after 'pianista'.