This builds focus is to leverage one of the most powerful support items in the game: Ardent Censer

Sona with her Aria of Perseverance is pretty much the only champion which can consistently & easily apply the Ardent Censer buff to all her 4 allies and refresh it in under 6 seconds.

Each ally buffed by Ardent Censer gets stats worth 1000g to 1750g, depending on level. That's huge value and not even accounting the on-hit healing. Teams where all 4 allies strongly benefit from the attack speed and on-hit are not uncommon (e.g. Fiora top, Ekko mid, Warwick jungle). In the dream scenario at level 18 your allies get a total of 7000g value, which is roughly worth 2 Trinity Force items.

Of course in practice the benefit will usually be much less, but still powerful enough to make a big difference. Together with Windspeaker's Blessing you have a strong utility foundation. I'm currently platinum and employed this build on many occasions with high success.

There's one small problem: your Aria of Perseverance has a prohibitive 100 mana cost at max level.

The solution: Tear of the Goddess. For a very modest 750g you get the awesome power of "manaless" Sona. To just name a few advantages that come with "manaless" Sona:

1. Roam with your team around the map at +15% speed or more whenever you want
2. Use your Diminuendo (and other Power Chord) much more frequently (almost-exhaust every 6 to 18s, without slow, but 0.5s longer, gimme that!)
3. Keep everybody healthy when taking (or attempting) objectives or pushing after a won fight
4. Use W pre-emptively when you think a fight may break out, to Ardent Censer buff allies
5. Less time wasted backing with a few hundred gold
6. In general you'll be able to do things not possible with a limited or depleted mana pool

To illustrate how relatively little gold 750 is: Redemption's HP and Mana regen stats (which are both unneeded for this build) have a combined worth of 850g.

Many supports like to build Warmog's Armor on Soraka, because it pretty much offers limitless heals. Tear of the Goddess on Sona is similar in its endurance. Instead of raw direct healing, she delivers a combination of 7 combat buffs (speed, shield, healing, armor, MR, attack speed, two sources of on-hit damage).

For damage-oriented Sona builds I would not recommend Tear, because they don't need as much mana. Unfortunately DMG Sona has a hard time with tanks, because she usually can't get penetration soon enough. Furthermore she has to take risks for full Lich Bane effect.

With this utility build you stay farther back. So I see no reason to buy anything else than Tear of the Goddess! That's after experimenting with many different builds over the past years. No other 750g investment would give comparable power and flexibility.

Nothing is set in stone here. Usually you want to have W maxed first though, because it is the core idea behind this Ardent Censer build, so you want full strength on Aria of Perseverance ASAP.

Putting a few points into Q early is useful for stronger poke. Grabbing E earlier may be wise against a bot lane with high kill pressure.

Windspeaker's Blessing is essential; other masteries & runes are personal preference.

Since this build focuses on utility, I put no points in the Ferocity tree. I prefer Veteran's Scars over Runic Armor , because recovering HP is usually less of a problem (especially with plenty mana) than burst damage. Both are good though. Fearless would help a bit against burst damage, but Insight is just too good.

Personally I like Seal of Scaling Health, because they break even with the flats at level 6 already, but it rarely makes a difference anyway. Level 2 all-ins aren't necessarily Sona's cup of tea.

Usually I finish the core build with Seraph's Embrace before building for the 2 remaining slots. The extra 110+ AP will increase the power of all your abilities significantly, while also giving you a nice emergency shield. Notably Song of Celerity will feel absolutely amazing for you and your team mates. And you can spam it :)

If the game isn't finished at this point I like to build a defensive item. The old Banshee's Veil would have been ideal, because it also offered health and MR (the two stats Sona lacks most, besides speed). New Banshee's Veil is still good on her of course, if there are strong AP threats.

For this build I would not recommend Redemption because the HP regen is virtually useless and also further mana regen isn't needed at this point.

Locket of the Iron Solari is gold inefficient (76%), so making good use of the active is key. On the other hand Locket's brother Banner of Command is 116% gold efficient, while the 400 mana give you an extra 12 AP worth 261g (due to Archangel's Staff).

• In team fights you want to stay a bit further back and use mainly W and E, because Q will usually have little effect on their front line and temporarily disable your Boots of Mobility
• Often Song of Celerity is better at mitigating damage than Aria of Perseverance, because the speed helps dodging skill shots
• Speed is your main defensive stat. With Boots of Mobility, Ardent Censer and Song of Celerity you are likely to be the fastest thing on the map (despite low 325 base speed)
• Diminuendo (Power Chord - W) is a very powerful ability, as already said. Don't forget to use it, usually on the closest target trying to engage. With your finished core build (~230 AP) it reduces its target's damage output by about 35%! That's just 5% less than Exhaust but 0.5s longer!
• Since you have no mana problems, use Aria of Perseverance whenever you think a fight may break out just to buff your team with the Ardent Censer stats and charge Power Chord.
• With boots of mobility you are often able to place a good enough Crescendo without flash. As a rule of thumb I'd say use flash to either save your skin or make a very decisive impact, but in case of doubt save it.
• When clearing minions 1 or 2 W on your allies is often enough to restore them to full HP, thanks to the Ardent Censer 6s long health drain
• Sona loves long, back and forth fights, especially with this build. Champions like Ekko or Lee Sin have good synergy with such an approach.
• Starting Spellthief's Edge plus Faerie Charm is usually fine, because as long as you have mana you also have healing available
• A part of the strength of this build lies in its late game power. It is a ticking time bomb, a bit like Nasus. When your grouped, healthy and buffed team swarms and probes enemies with +20% speed and constant shields, dances back and forth... sooner or later an opponent will lose patience. Right into your R, Diminuendo and Exhaust. Time plays in your favour. In many aspects, not only the sustain and natural Sona CDR scaling.
• Like a Thresh who throws back his lantern to fake a gank, you can sometimes use Song of Celerity as a psychological tool, to gauge their strength & willingness to fight, make them less alert when the real gank comes etc.
• As a utility support in a typical match 3 deaths or less is just fine
• In general try to be safe, but ready to react to engages, while ideally also being in a position to support your initiator(s) with buffs, Diminuendo de-buff or Crescendo

There are many good build paths for Sona. Tear of the Goddess builds have been around forever, but it is the addition of Ardent Censer which makes them really shine.

Sona plays music, magic energy is her fountain and while the tears of the Goddess pour down she plays her tunes on and on and on...