First off, big respect for your post and aspirations.
I work with a wide range of adults with severe to mild learning disabilities and/or autistic. We are lucky to have a team of music therapists - in a nutshell, they have psychology degrees because they are using music to support people who have communication and emotional difficulties in a therapeutic and clinical way (there is so much more to it than that, but like I said, in a nutshell).
However, there are many volunteers who come to our organisation to play music either with or to the people we support. I can’t stress enough how VITAL this is to a large amount of people. Again in a nutshell, a staggering number of people in residential care spend large proprotions of their day disengaged and devoid of opportunities. Generally this is due to the social care finanial crisis affecting community outlets and organisation’s support provisions and also because many services can struggle to convert their values into staff behaviour. People that come in to do music engage people, make their day, and often give them something else to look forward to. I’ve also seen this have a great impact on staff, and act as a much needed stress reliever for them too. Less stressed staff equals happier supported people.
I could go on and on, especially as this touches on my professional remit, however I’ll end by saying that by going in and playing with or for people you’ll be making a significant contribution to their quality of life outcomes.
A good organisation will have a volunteering person/department, will have a meeting with you, get you DBS checked and will make the most of your kind offer. Just reach out and find the right place. Good luck!