Many of the tunes we learn in KS1 and KS2, as well as our first tunes at KS3, involve straight harp technique. This means we are playing songs in the key of the harmonica, usually starting and ending on a blow note.
In time we discover that we can start and end songs using draw notes and, in doing so, we begin to learn the art of positional playing. This is sometimes called modal playing. In simple terms, it enables us to explore different keys and create new musical flavours.