Phrase =
海选 (open audition) +
中 (in the midst of).
海选 itself rose to fame around 2005 with Super Girl (《
超级女声》); literally 'sea selection' — the candidate pool is as wide as the sea. As a segmenter token
海选中 is technically
海选 + locative
中, not a single word, but it appears frequently as a fixed phrase meaning 'in the audition phase'.