-PowerChord-
what you really want to know is that after 3 shot you get the power chord,[after casting 3 spells, Sona's next attack deals bonus magic damage. Additionally]
you need to keep this in mind. So what you do is Always keep 2 Chord's up if an EnemyPlayer tries to engage in to a fight

early game... heal your lany or damage the enemy and shoot your power chord at him this will do some pretty damage
when reaching 6 you get your ultimate this is an OAE stun, here we do the same thing we try to keep 2 chords up at before entering a battle, we shoot or crescendo at the group of enemy's and automatic we get our 3chord that gives us the powerchord to boost some damage.
lich bane and our powerchord have an nice synergy as it procs together

with this guide they have extremely good opportunities to carry their ad on your side of the lane to win but they forget to stay with their wards not saven

After...

When your team engages with the other team into an Teamfight its a great idee and it should be an automatic reaction to pres R when you see that you can stun 3 or more,
also when youre teammate gets focused in lane and he/she wont survive shoot your Ulti and try to hit as much as posible enemy's to stun them and get your teammate to the safety of the tower.
when they try to turretdive you don't hesitate to try stunning the divers at turret. they wil receive additional dmg of you and the turret if you manage to clear the creeps fast enough.

song of celerity
if you see your teammate is in problem and being chased by several other enemy's run slightly towards him and keep spamming this spell he will get extra speedbonus of your auro but also get an Bot(Buff over Time) increasing his speed 6/8/10/12/14% for 1,5 sec
it will defently safe his or their lives and also yours.