Constant Note Blocks

Using the same crafting recipe as a standard Note Block, but substituting the redstone with an amethyst shard, you craft a Note Block featuring a purple diamond in the center. This block interacts with redstone in the following way:

It produces the same sounds as a standard Note Block, but instead of merely triggering a sound upon receiving a pulse, it can sustain the note as long as the signal remains active. The volume of the note varies depending on the signal strength.

This volume mechanic could potentially be applied to standard Note Blocks as well.