Currently, the relation between the MultiSelect input and its TagList element (the one that holds the selected items) is established with an aria-describedby attribute. That results in the screen readers to report the selection (all selected items) as one line of text which doesn't adequately describe the control or and its context. The text of each selected item is announced but it is not clear how many items are selected. Also, there is no articulation between each item text that is announced.
Consider and implement better relation/structure, so that the context of the widget (the selected items and their number) is announced clearly.
Also, I have tested the navigation between the drop-down and the tag list in the MultiSelect with NVDA on Firefox and CromeVox on Chrome. In both cases when navigating from the drop-down to the tag list (using the left arrow) the screen readers properly announce the active tag list item, its position in the tag list (2 of 2, for example) and the fact that it can be deleted. They, however, do not announce the active item when navigating back to the drop-down (using the down/up arrows).
Regards,
Veselin Tsvetanov
Progress Telerik