Piano (TV)

Piano lovers may have been disappointed in the lack of "true" piano playing in Piano, and thus, I recommend Nodame Cantabile. 

Music and romance anime. Both series deal with a piano player who lost their way. Unable to play the piano. But thanks to their friends/sensei, they were able to play again. Classical music can be heard in both series.  

two anime about starting to grow up (romance, school, etc.) slow-paced focused on characters and relationships rather than action 

Musical moe anyone? Piano is a more serious anime whilst K-On is more outrageous. 

Same slice-of-life pace and a realistic setting. Both are about the fairly ordinary life of a young girl.  

Both are "Slice of Life" shows, that are slow paced, have very little plot, a bit of drama (and very small hints at romance), both involve a group of friends and their relationship with the lead character (Piano Main Character: Miu Nomura ||| To Heart Main Character: Hiroyuki Fujita). Both shows lack action, and have a very limited use of humur. Both shows have a bunch of interesting characters (that don't do anything interesting the entire series), and both shows can be considered "coming of age stories". Also both To Heart and Piano are realistic (well To Heart has some non-realsitic parts). However both shows are different takes on this genre. To Heart follows a male lead, while Piano follows the female lead. If you like To Heart, watch Piano! If you like Piano watch To Heart! read more 

Both coming-of-age slice of life anime exploring characters and the conflicts within them as they stand at the threshold of adolescence. Also the exploration of young girls as they grow towards understanding romance.