its all just music and lyrics...

 some songs are obvious with the lyrics and just straight up sing about their alter ego like for example Blu Nyle, with the song Alter Ego...

 

however their are some that do have hidden meanings within the song, the lyrics are screaming for their alter ego to come out and save them, however never really asking...  

 

Jessie J with the song Who You Are, relates to herself and her alter ego... putting on a disguise that sometimes she cant even recognise herself.

 song lyrics all in some way have hidden meanings....