The fact that the parent who abandoned Ricky was the only one able to speak directly to him makes me reconsider my opinions about Lynne and how she could have a redemption and how Mike is not a good father either.
In conclusion, Ricky has terrible parents
What if...
Lynne taught Ricky how to play the piano, which is why she has a piano in the room that she has prepared for Ricky in her apartment.
I think sometimes Lynne goes there to play music and think about how she was a bad mother and how she wants to change that.