Given the task definition and input, reply with output. This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

Composers of classical music have often made use of folk music (music created by musicians who are commonly not classically trained, often from a purely oral tradition). Some composers, like Dvořák and Smetana, have used folk themes to impart a nationalist flavor to their work, while others like Bartók have used specific themes lifted whole from their folk-music origins.
Folk musicians are not commonly what?