Keep going with your speech therapy exercises....they may seem daft but it's all about keeping the brain pathways connected to support making the sounds, and keep a flow of speech and keep the breathing going right to help the vocals work to the best that they can.
I work with speech therapy with children with speech issues....and helped my Mum with the exercises her speech therapist left her with.
So keep going!! Shout and oooooo and eeeee and aaaaa and sing!!