Ways to use Kazumi's Note of Preservation

[Rodeojones1979]

This weekend I completed 60% of level 59 through some intense and successful XP grinding. For the first time since I rolled this toon in 2011 the end appears in sight. So now I'm considering what gameplay looks like for an un-epic'd but lvl 60 bard. Naturally, I've never used Kazumi's Note of Preservation (a group DA). And I'm interested to learn about its best uses and various tricks you can do with it.

First, are all group members unable to attack, cast, etc when the song is played?

Is this song only good for preventing wipes? Should it be used when tanks or about to flop? Can I use it to prevent the chanter from dying from a charm break?

What's a good use for this song when soloing?

How often do you leave this song memmed?

What other ways do you use this song? What clever ways can it be applied?

Thanks!