Greetings rebornfree and lismore,
Agreed that use of music and simple lessons are often the best ways to go here. One of our ministers recently was providing lessons to an individual under generally similar circumstances, it was not Alzheimer's but one of the other forms of dementia (I believe it may have been vascular dementia or similar, apologies as I'm not too versed in the medical terminology).
He was facing generally similar challenges, the key he found was to break things down and keep them simple. And where needed, to start with the verses and teachings that were easier to grasp, and then build little stories and examples from there that were easier to follow. As analogy, many Biblical concepts and teachings are quite challenging even for Biblical scholars, hence the detailed exegesis and multiple levels of interpretation in seminaries and commentaries, to make the concepts relatable and understand the underlying and varied meanings. So there's nothing inherently awry with challenges in communicating difficult teachings, especially for individuals with cognitive challenges as well. In his case talking with the church member with vascular dementia, he would often start with a verse from ex. Psalms or Corinthians that might be more familiar or easier to grasp, and then build out from there, not unlike a carefully put together but simple Sunday school lesson. And yes music helps! Especially if the person being addressed has musical experience or loves to sing, one of our chaplains mentioned this is often good way to reach individuals as this part of their minds functions well even with dementia. Gospel music often works well. We've also found some simple, moving hymns work very well.