Sona: One rework to rule them all?
Now, before I post my ideas, I am aware that many people have already suggested ideas for another Sona rework. Also I'm sure many people will say "omg stop whining, lots of champions needs VUs/reworks more than her, and she just got one", and I won't try to deny that there are lots of champions that are in urgent need of kit and visual reworks (Taric, Morde, Poppy). But I honestly believe the rework didn't solve any problems that Riot saw in Sona, other than that they thought she was too passive. All the rework did was remove her stance-mechanic in favor of small buff zones that aren't fit for a champion that would rather stay in the back line due to her squishiness. So, I propose we return to the stance-auras, but in a way that requires thought and decision-making rather than QWEQWEWQEQE to try to always have 3 buffs up like she was pre-rework.
So, with that in mind, let's get started:
Passive- Power Chord: After casting 3 basic abilities, Sona's next basic attack will deal 13 / 20 / 27 / 35 / 43 / 52 / 62 / 72 / 82 / 92 / 102 / 112 / 122 / 132 / 147 / 162 / 177 / 192 (6 + 7 / 8 / 9 / 10 / 15 at each level) (+ 20% AP) bonus magic damage, with an additional effect depending on the last basic ability cast.
I actually think Sona's passive is healthy, and doesn't require changing at all, so it's the same.
Q- Brio: (Range 800) (Cost 50/60/70/80/90) (Cooldown: 10) Active:Sona emits 2 bolts of sound that converge on the target location and fan beyond it up to a maximum range, each bolt will deal magic damage to enemy units and will stop on the first champion hit. Champions hit by a second bolt take 50% damage from it; minions take 50% damage from each bolt. Sona can cast Hymn of Valor within the next 3 seconds. Magic Damage: 50 / 80 / 110 / 140 / 170 (+ 40% AP) Maximum Magic Damage to Champions: 75 / 120 / 165 / 210 / 255 ( +60% AP)
Powerchord-Staccato: If this spell was last cast when Power Chord is ready, Power Chord deals 20%/35%/50%/65%/80% bonus damage.
Hymn of Valor (Toggle): (Range 1000) (Cost: 2 / 4 / 6 / 8 /10 mana per second) Sona and allied champions tagged with Hymn of Valor's aura gain Attack Damage and Ability power. [Sona must un-toggle the aura before being able to cast Brio again] Attack Damage and Ability Power (Allies): 3 / 6 / 9 / 12 / 15 (+ 10% of Sona's Attack Damage) (+ 4% Sona's Ability Power) Attack Damage and Ability Power (Sona): 3 / 6 / 9 / 12 / 15
One of the things many people complain about is Sona's simplicity, but they're not necessarily right in that 'easy' champions shouldn't be strong. The problem with Sona's Q has always been that it's auto targeted, so there's not much interactivity going on whenever you use it. I feel that changing it into a Heimer/Lulu-esque skillshot will open up a lot of options for both Sona and her laning enemies. You can now dodge her only poke ability, but you will take quite a bit of damage if you don't. However, one of Sona's weaknesses has always been her crap wave-clear, so I reduced Q's damage towards minions.
I'll talk about the aura at the end of the post.
W- Animato: (Range 800) (Cost 80 / 90 / 100 / 110 / 120) (Cooldown: 10) Active: Sona heals a target allied champion and herself. The healing is increased by 1% for every 1% of the target's missing health. If Sona heals herself only, the heal will be 20% more effective. Sona can cast Aria of Perseverance within the next 3 seconds. Heal: 35 / 60 / 85 / 100 / 125(+ 25% AP) Maximum Heal: 70 / 120 / 170 / 200 / 250 (+ 50% AP) Self-Heal: 42 / 72 / 102 / 120 / 150 (+ 30% AP) Maximum Self-Heal: 84 / 144 / 204 / 240 / 300 (+ 60% AP)
Powerchord- Diminuendo: If this spell was last cast when Power Chord is ready, Power Chord will also reduce the target's damage output by 35% (+ 3% per 100 AP) for 3 seconds.
Aria of Perseverance (Toggle): (Range 1000) (Cost: 2 / 4 / 6 / 8 /10 mana per second) Sona and allied champions tagged with Aria of Perseverance's aura gain Armor and Magic Resist. [Sona must un-toggle the aura before being able to cast the Animato again] Armor and Magic Resist (Allies): 3 / 6 / 9 / 12 / 15 (+ 10% of Sona's bonus Armor) (+ 10% of Sona's bonus Magic Resist) Armor and Magic Resist (Sona): 3 / 6 / 9 / 12 / 15
Her W is mostly the same. I borrowed some elements from Taric; Sona can now choose who she heals, and can even choose to only heal herself for a slightly stronger heal. It's not instantaneous like Taric's, however; it will still need to travel like it currently does, so it can be blocked by things like Yasuo's windwall. I took away the shield because it's not something that needs to be on a heal. All that does is limit the clutch-power Sona's rework was supposed to have; being able to save low-health allies but be bad at topping off was what Riot stated they wanted Sona to do. Returning the %missing health ratio back to 1:1 now helps Sona's heal actually feel impactful without having to build absurd amounts of AP.
I'll address the aura portion at the end.
E- Allegro: (Range 800) (Cost 65 / 70 / 75 / 80 / 85) (Cooldown: 10) Active: Sona sends sounds to a targeted location, leaving a 400-range field for 2.5 seconds that speeds up allied units. The effect diminishes 2 seconds after leaving the area. Sona can cast Song of Celerity within the next 3 seconds Initial Movement Speed: 20% / 25% / 30% / 35% / 40% (+ 5% per 100 AP)
Powerchord- Tempo: If this spell was last cast when Power Chord is ready, Power Chord will also Slow the target by 40% (+ 5% per 100 AP) for 2 seconds.
Song of Celerity (Toggle): (Range 1000) (Cost: 2 / 4 / 6 / 8 /10 mana per second) Sona and allied champions tagged with Song of Celerity's aura gain flat Movement Speed. [Sona must un-toggle the aura before being able to cast Allegro again] Movement Speed (Allies): 9 / 12 / 15 / 18 / 21 (+10% Sona's bonus Movement Speed) Movement Speed (Sona): 9 / 12 / 15 / 18 / 21
I borrowed elements from Orianna and Karma's E for this one. Sona's E has always felt like her most lackluster ability; making it a 'skillshot' field I feel will help give her more interesting uses for her speed boost.
Again, I'll address the aura towards the end of my post.
R- Crescendo: (Range 1000) (Cost 100/150/200) (Cooldown: 140 / 120 / 100) Sona plays an irresistible chord in a line, dealing magic damage to enemy champions and charming them for .75/1.25/1.75 seconds. Magic Damage: 150 / 250 / 350 (+ 50% AP)
This doesn't need to happen, but I always thought that, thematically, 'stunning' enemies with an "irresistable chord" didn't make much sense. Charm-cc made more sense in the way that they'd be drawn to Sona more; but I guess if it were a charm they wouldn't be able to dance in place. I don't know, it's just an idea I had, it's not really important.
Now, about her auras. You may notice that it's now a toggle, sort of like Swain I guess. I think this will help alleviate the problem that old Sona had; try to spam your abilities so you always get all 3 buffs. Now you can choose which buff you need while still being able to use other abilities. Are you getting sieged under your turret and need a little bit more defense? Activate your W aura. Did you ace their team and need to high-tail it to an objective? E aura.
I gave the auras mana costs to balance out the fact that they now scale with various things.
I could have made them just all scale with ability power, but that wouldn't help Sona's current problem; she needs tons of AP to be useful. Before, I loved building Mikaels and Aegis and Utility items, but doing that now just makes your active abilities much less impactful because her base numbers are so low. Giving them different scaling opens up a lot more STRATEGIC DIVERSITY, you know, Riot's "philosophy" this season?
Did your team choose a lot of Attack Damage? 
Does their team have a lot of Magic Damage?
Do you have a Hecarim on your team?
+ E for lots of movement speed and AD
One of the downsides is that she will need a bit more mana now, so things like
may be needed.
One last thing I did was make all her cooldowns 10 seconds, instead of 8,10, and 12. I think this will help make her feel more fluid like before, as well as preventing any 'oppressive' poke.
TL;DR Please take the time to at least skim over everything, I don't really know how to summarize these changes