I hope you are doing well! It sounds like Siram is doing great! We are so excited for you all in your Son-Rise Program journey with him. So to answer the first part of your first question, I think it needs some experimentation. If he is burying himself in the couch and asking you to sing then it seems that his eye contact would be low or non-existent at that time. I would start with requesting eye contact in a fun way (e.g. "Hey you! Look at me so I can sing for you!") also vary this by telling him "The longer you look, the longer or the louder I sing the song for you!". This will help him to connect in a deeper way with you while you sing. This is a stage one eye contact goal in our Son-Rise Program Developmental Model "Looks to start and continue the interaction".
If he is already looking, or you have done the above and he responds nicely to the request then you could find other ways for him to participate in a physical way. Instead of always asking him to sit up, experiment with having pretend buttons that he could press that make you sing each song (e.g. put some stickers on you face so he can come and press them). Or you could the write the song names on pieces of paper and stick them up around the playroom on the walls and you both run to the next song to sing for him. That will get him up and moving around and not just burying himself in the couch.
The second part to your first question will be if he doesn't respond to your requests and invitations to look or participate then I would stop singing and join by pretending to bury yourself in your own couch, maybe you could get some cushions to do this with and create your own experience. If he's not responding then he's clearly not available and is being more exclusive so it's time to join until you get a stronger green light.
Here is a link to my latest blog that talks about interactions and different things to work on in them.http://blog.autismtreatmentcenter.org/2 ... -with.html
The other question about the headphones. We suggest you don't have him listen to music right now. Anything electronic, music, video games, TV, etc will have a hypnotic effect on him that can be over-stimulating and hard to compete with when we are helping him want to be with people more in his life.
Try setting him up with other toys or a game he could play with in the evenings that is not electronic in that way.