Suppose you went to a dance but didn’t dance, did you enjoy it as much, did you get as much out of it if you danced.
If you went to class and didn’t write down any notes, or take the tests, but just answered the questions in your head, are you likely to take with you as much if you did fully participate.
I know you sound like you are uncomfortable with your singing voice but one of the great saints of our church says that singing is praying twice.
And as far as speaking the words of the mass means that you are fully participating in the sacrifice offered up for us. You are more likely to become more focused on what is actually being said and done and less likely to become distracted as well. Try it…It’s not a sin not to fully participate but why wouldn’t you want to if you would get so much more out of it. We are told to fully participate, not wait and be entertained by others singing and praying.
It may be uncomfortable at first. No one expects you to cantor for the mass, or even sing loudly, but turn to the page of the song and begin to mouth the words, then sing them softly so you and perhaps the person next to you can recognize that you are singing. Always, repeat always, pray aloud the prayers with the full congregation You will see immediately the difference in your prayer life as well. As Jesus said…Do not be afraid!