If you're looking for anime similar to Hatsune Miku: Unofficial Hatsune Mix, you might like these titles.
Miss Monochrome, an idol who lives in a luxurious castle with her trusty Roomba companion, wants nothing more than to be back in the spotlight like the popular idol Kikuko. But the road to stardom will be fraught with challenges, from finding a trustworthy manager, to getting bit parts on TV, to even getting the media to notice her glorious talents and amazing feats!
Who doesn't like a robot who sings? Well, that is the definition of these two series. Miss Monochrome following the life of a robot in random adventures in each episode whereas Hatsune Mix is about the Vocaloid Hatsune Miku and her friends in their everyday life. Both don't have much of a story, but these random elements come across as quite cute. Like I said the characters are quite similar, plus have aspects of music and idols for those who like it. If you enjoyed the Miss Monochrome anime and want more of this randomness then check out this manga, and vice versa.
Chika, Matsuri, Miu, Ana and Noboe are back, and ready for more slow-paced misadventures! All Noboe wants to do is get a job, but the obnoxious and interfering Miu will not have such a thing. Meanwhile, Matsuri is being taught to be a leader with the help of a… horse head?! Ana can no longer hide her Japanese-talking secret, the whole crew mess around with bunny ears and lion costumes, and trips to the library and school abound. It’s just another day in the life of these friends!
Chiko, Ana, Miu and Matsuri are back once more for a variety of misadventures. When Miu declares she wants to be an idol and then knocks herself out, she awakens in between the realms of Heaven and Hell with her friends as guides to the underworld. Beyond that the girls deal with prank calls and do their best at independent study, amongst other things. As always, they have plenty of fun in the process!