A member of our church recently suffered a stroke, which has left him with aphasia. He's physically recovered but is, for now, barely able to speak. Speech therapy is helping but it's gruelling, and slow.
I heard today that, while he can speak only a few words, he can sing hymns. Hymns have always been important to him: he tells of growing up in a Methodist church where congregational singing was central, and he seems to know the words to all verses of all the works in the hymnal. The hymns, with their words, are at his fingertips still. The first he sang, having heard it at an online service, was a very old one: "O God, our help in ages past."
Another parishioner reported that the same thing had happened to his grandmother: most confusingly to her grandchildren she could only sing. Apparently different parts of the brain are used in language use and music, and in cases such as these the words are remembered as an integral part of the melody.
We pray our friend soon recovers full power of speech. But in the meantime it's a strange and wonderful comfort to think that hymns, so dear to him, will support him on the way.