One contemplates its beauty and is moved in reaction to it. One identifies with it as it expresses emotions and lets those emotions wash over one. Sticking with music, examples of objective art would include Bach and the baroque composers generally. Examples of subjective art would include Beethoven and the romantics generally. Rock 'n' roll is overwhelmingly a subjective form.
Jazz is largely objective.
Although there are musicians of both types in all periods, the balance in the last 200 years has very much tipped toward the subjective. C.P.E. Bach, one of J.S. Bach's four musical sons, championed the theory that the sentiments should be captured in music. I'm not sure what Popper believed on the subject, but I don't think the two categories are mutually exclusive. Composers like Mozart, Haydn and Schubert seem to embody both principles, although in different proportions at different times. Popper does seem to have believed that people gravitated toward one or the other extreme of art according to their personality.