ZITHER! is fun and incredibly useful when played defensively, as a buff-monster.
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Hometown Anthem (Cold Cold Cold) should always be your active song, and basically spammed - run with your team and keep playing it. Feel the Crowd gives you a +50% Mana regen rate when near your team, so it's fairly self-sufficient. You're like a well of Barrier that way, and synergizing with Strength of the Spirits and Knight-Protector, it becomes quite impeccable. Also, if you learn Winter Music, every Cold chord you have lined up grants you a defense buff.
The longer lasting buffs, such as A Little Knight Music and Sing-Along, as well as Battle of the Bands should be renewed whenever possible - in this order of priority.
If you always stay with your team for extra regen (and reach obviously), time it correctly with basic attacks to benefit from Opening Set, you should always have enough Mana to keep your team Barriered, 20% Attack Speed Bonus, Heal on Kill, Heal on Hit, and +150 Armor bonus (with any halfways decent staff) at all times.
The guy is ridiculous, and I cannot help myself but seriously question Maryden's taste in men.
"I know a place in Val Royeaux, where you can get covered in leaf gilding, and then polished. Who's with me?!"