Because Sona cannot speak the responses here are taken as magical telepathy. This is evidenced by her 'external' interactions (taunt, joke) being musical cues rather than words.
Champion Select
Pick
Sona plays a collection of notes on her etwahl.
Ban
Sona smacks her hands on her etwahl.

"Her melody moves the soul, her silence sunders the body." - SwainSquare Jericho Swain, after attending her concert
SonaSquare Sona has no memories of her true parents. As an infant, she was found abandoned on the doorstep of an Ionian adoption house, nestled atop an ancient instrument in an exquisite case of unknown origins. She was an unusually well-behaved child, always quiet and content. Her caretakers were sure she would find a home quickly, but it soon became apparent that what they mistook for uncommon geniality was actually an inability to speak or to produce any sound whatsoever. Sona remained at the adoption house until her teens, watching in hopeless silence as prospective adopters passed her by. During this time, the caretakers sold her unusual instrument to anxious collectors, hoping to build her a trust. For a myriad of bizarre and unexpected reasons, however, it would be returned, or simply appear again outside the house.

When a wealthy Demacian woman named Lestara Buvelle learned of the instrument, she immediately embarked to Ionia. When the caretakers showcased the instrument for her, she rose wordlessly and explored the house, stopping outside Sona's room. Without hesitation, Lestara adopted her and left a generous donation for the instrument. With Lestara's guidance, Sona discovered a deep connection with the instrument which Lestara called an 'etwahl'. In her hands, it played tones which stilled or quivered the hearts of those around her. Within months, she was headlining with the mysterious etwahl for sold-out audiences. She played as though plucking heartstrings, effortlessly manipulating the emotions of her listeners - all without a single written note. In secret, she discovered a potent and deadly use for her etwahl, using its vibrations to Hymn of Valor slice objects from a distance. She honed this discipline in private, mastering her gift. When she felt prepared, she went to the only place which could offer her a fitting recital: the League of Legends

Patch History
V9.21
Power Chord Power Chord
NEW EFFECT: When Power Chord is ready, her resource bar now changes color based on her current active aura.
BUG FIX: Her abilities no longer fail to generate Power Chord stacks immediately after an empowered attack.
V9.20
Power Chord Power Chord
NEW EFFECT: Added a resource bar so that it's easier for Sona to track her own passive (only visible to her).
V9.13
Hymn of Valor Hymn of Valor
Aura damage AP ratio reduced to 20% AP from 30% AP.
Song of Celerity Song of Celerity
AP ratio reduced to 3% per 100 AP from 6% per 100 AP.
V8.9
Stats
Base attack damage increased to 49 from 46.
Power Chord Power Chord
Base damage increased to 20 − 240 (based on level) from 15 − 235 (based on level).
V8.7
Sona DJCircle DJ Sona
BUG FIX: Concussive form VO lines are no longer cut off when played.
V8.3
Stats
Base health regeneration increased to 5.5 from 5.424.
V8.2
Hymn of Valor Hymn of Valor
Mana cost reduced to 50 / 55 / 60 / 65 / 70 from 60 / 65 / 70 / 75 / 80.
V7.24
Hymn of Valor Hymn of Valor
Mana cost increased to 60 / 65 / 70 / 75 / 80 from 45 / 50 / 55 / 60 / 65.
Base on-hit magic damage reduced to 10 / 15 / 20 / 25 / 30 from 20 / 30 / 40 / 50 / 60.
On-hit magic damage AP ratio increased to 30% AP from 20% AP.
V7.23
Aria of Perseverance Aria of Perseverance
BUG FIX: Fixed a bug where multiple instances of the same shielding effect were stacking, rather than refreshing. This bug mostly occurred at high levels of CDR.
V7.22 November 12th Hotfix
Stats
Base armor reduced to 28 from 30.
Base attack damage reduced to 46 from 50.04.
Aria of Perseverance Aria of Perseverance
Base heal reduced to 30 / 50 / 70 / 90 / 110 from 35 / 55 / 75 / 95 / 115.
Base shield strength reduced to 25 / 50 / 75 / 100 / 125 from 30 / 55 / 80 / 105 / 130.
V7.22
Stats
Base armor increased to 30 from 20.544.
V7.16
General
Texture update to Sona PentakillCircle Pentakill Sona.
V7.12
Sona DJCircle DJ Sona
BUG FIX: The tail end of her recall SFX now play consistently.
V7.9 May 4th Hotfix
General
NEW EFFECT: Attack animations have received non-gameplay impacting adjustments.
Power Chord Power Chord
NEW EFFECT: Sona now uses crit animation while under the effect of Power Chord.
V7.9
Stats
Magic resistance growth increased to 0.5 from 0.
V7.5
Sona DJCircle DJ Sona
BUG FIX: No longer stops moving after switching tracks.
V7.3
Sona ArcadeCircle Arcade Sona
Aria of Perseverance Aria of Perseverance
BUG FIX: Shield particles now correctly disappear when the shield is broken.
V7.2
General
BUG FIX: Fixed a spectator bug where after skipping forward or backward, Ethereal DJ Sona would sometimes leave disembodied chunks of her gear on the map.
V6.16
General
BUG FIX: Arcade and DJ Sona aura VFX have been increased in size to match her recent gameplay changes.
Song of Celerity Song of Celerity
Self movement speed reduced to 10 / 11 / 12 / 13 / 14% from 13 / 14 / 15 / 16 / 17%.
Aura movement speed AP ratio reduced to 6% per 100 AP from 8% per 100 AP.
Crescendo Crescendo
Basic ability cooldown reduction reduced to 10 / 25 / 40% from 20 / 30 / 40%.
V6.15
Aria of Perseverance Aria of Perseverance
BUG FIX: Fixed a bug where Aria of Perseverance could be cast instantly after Song of Celerity, rather than being gated behind Sona's brief "global cooldown" after casting a basic ability.
V6.14 July 20th Hotfix
Aria of Perseverance Aria of Perseverance
Heal reduced to 35 / 55 / 75 / 95 / 115 from 40 / 65 / 90 / 115 / 140.
Song of Celerity Song of Celerity
Bonus movement speed reduced to 13 / 14 / 15 / 16 / 17% from 16 / 17 / 18 / 19 / 20%.
V6.14
General
Aura radius increased to 400 from 350.
Aura duration no longer extends for up to 2 seconds when affecting allies.
Power Chord Power Chord
Base damage increased to 15 − 235 (based on level) from 13 − 192 (based on level).
Hymn of Valor Hymn of Valor
Base damage reduced to 40 / 70 / 100 / 130 / 160 from 40 / 80 / 120 / 160 / 200.
Aria of Perseverance Aria of Perseverance
Base heal increased to 40 / 65 / 90 / 115 / 140 from 30 / 50 / 70 / 90 / 110.
Heal AP ratio increased to 25% AP from 20% AP.
Base shield health increased to 30 / 55 / 80 / 105 / 130 from 35 / 55 / 75 / 95 / 115.
Shield AP ratio increased to 30% AP from 20% AP.
REMOVED: Increased healing based on missing health.
Aria of Perseverance Diminuendo
Target now deals 25% less damage for 3 seconds, up from 20%.
AP scaling increased to 4% AP per 100 AP from 2% AP per 100 AP.
NEW EFFECT: Now shrinks targets for duration of debuff.
Song of Celerity Song of Celerity
Active self movement speed increased to 16 / 17 / 18 / 19 / 20% movement speed for 3 seconds (and up to 7 seconds if Sona is out of combat) from 13 / 14 / 15 / 16 / 17% decaying over 3 seconds.
Aura movement speed AP ratio increased to 6% per 100 AP from 4% per 100 AP.
Aura movement speed duration increased to 3 seconds from 1.5.
Crescendo Crescendo
REMOVED: Increases potency of basic abilities.
NEW EFFECT: Grants 20 / 30 / 40% base cooldown reduction on basic abilities. Stacks multiplicatively with cooldown reduction.
V6.8
General
Splash artwork for Sona MuseCircle Muse Sona updated to the Chinese art.
V5.22
Stats
Mana regen increased to 11.5 from 9.
V5.5
Power Chord Power Chord
REMOVED: Being consumed on hitting Scrying Orb item Scrying Orb, Farsight Orb item Farsight Orb, or Sentinel Sentinel.
Crescendo Crescendo
Mana cost reduced to 100 at all ranks from 100 / 150 / 200.
V5.1
Stats
Movement speed reduced to 325 from 330.
Power Chord Power Chord
Hymn of Valor Staccato damage reduced to 40% from 50.
V4.21
Hymn of Valor Hymn of Valor
BUG FIX: First cast causing game lag.
V4.20
Hymn of Valor Hymn of Valor
On-hit damage AP ratio reduced to 20% from 25%.
Aria of Perseverance Aria of Perseverance
Heal increased to 30 / 50 / 70 / 90 / 110 from 25 / 45 / 65 / 85 / 105.
Modifier reduced to 0.5% of ally's missing health from 1.
Mana cost increased to 80 / 85 / 90 / 95 / 100 from 70 / 75 / 80 / 85 / 90.
V4.17
Hymn of Valor Hymn of Valor
Fixed a bug where the damage range was 700 instead of the intended 850.
V4.13
Visual and Gameplay update.
Texture update to all skins.
All auras' radius reduced to 350 from 1000.
Aura duration changed to 3 seconds from indefinite.
NEW EFFECT: Aura duration increased by 0.5 seconds each time Sona tags an ally.
Stats
Armor increased to 15 from 12.
Health lowered to 353 from 380.
Health growth increased to 77 from 70.
Power Chord Power Chord
Hymn of Valor Staccato damage reduced to 50% from 100.
Hymn of Valor Hymn of Valor
Base damage reduced to 40 / 80 / 120 / 160 / 200 from 50 / 100 / 150 / 200 / 250.
REVISED AURA: Sona and allies touched by the aura will deal 20 / 30 / 40 / 50 / 60 (+ 25% AP) bonus magic damage on their next autoattack within the next 5 seconds.
Cooldown increased to 8 seconds from 7.
Aria of Perseverance Aria of Perseverance
Heal changed to 25 / 45 / 65 / 85 / 105 (+ 20% AP) from 40 / 55 / 70 / 85 / 100 (+ 25% AP).
NEW EFFECT: Heal increases by 1% for every 1% of ally's missing health.
NEW AURA: Sona and allies touched by the aura gain a shield that mitigates the next 35 / 55 / 75 / 95 / 115 (+ 20% AP) damage for up to 1.5 seconds.
Mana cost increased to 70 / 75 / 80 / 85 / 90 from 60 / 65 / 70 / 75 / 80.
Cooldown increased to 10 seconds from 7.
Song of Celerity Song of Celerity
REVISED ACTIVE: Sona gains 13 / 14 / 15 / 16 / 17% (+ 7.5% per 100 AP) bonus movement speed, decaying to the aura bonus over 3 seconds.
NEW AURA: Allies touched by the aura gain 10 / 11 / 12 / 13 / 14% (+ 3.5% per 100 AP) bonus movement speed for 1.5 seconds.
Cooldown increased to 12 seconds from 7.
Crescendo Crescendo
NEW PASSIVE: Ranking up increases the strength of Sona's auras and Song of Celerity Song of Celerity's self bonus movement speed.
Hymn of Valor Hymn of Valor: + 10 / 20 / 40 extra on-hit magic damage.
Aria of Perseverance Aria of Perseverance: + 10 / 20 / 40 extra shield.
Song of Celerity Song of Celerity: + 2 / 4 / 6% bonus movement speed.
CLARITY: Animation updated to reflect both skillshot targeting and area of effect.
V4.9
General
New splash artwork for Sona PentakillCircle Pentakill Sona.
Texture update to Sona PentakillCircle Pentakill Sona.
V4.5
Stats
Armor increased to 12 from 11.3.
V4.2
Song of Celerity Song of Celerity
Fixed a bug where the tooltip showed a +4% per 100 AP ratio for both haste and slow.
Fixed a bug where the haste was only using 1% of Sona's AP instead of 2.
Fixed a bug where the slow was only using 2% of Sona's AP instead of 4.
V3.14
Hymn of Valor Hymn of Valor
AP ratio reduced to (+50% AP) from (+70% AP).
NEW EFFECT: Power Chord Staccato has a (+20% AP) ratio.
Aria of Perseverance Aria of Perseverance
Heal reduced to 40 / 55 / 70 / 85 / 100 from 40 / 60 / 80 / 100 / 120.
NEW EFFECT: Power Chord Diminuendo has a (+2% per 100 AP) ratio.
Song of Celerity Song of Celerity
Bonus movement speed changed to 4 / 6 / 8 / 10 / 12% (+2% per 100 AP) from 6 / 8 / 10 / 12 / 14.
NEW EFFECT: Power Chord Tempo has a (+4% per 100 AP) ratio.
Crescendo Crescendo
AP ratio reduced to (+50% AP) from (+80% AP).
V3.8
Stats
Base health increased to 450 from 410.
Base armor increased to 11.3 from 9.3.
Power Chord Power Chord
Damage changed to 13 − 192 (based on level) from 8 + (10 × level).
Aria of Perseverance Aria of Perseverance
Fixed a bug where Power Chord Diminuendo was not reducing the target's damage.
Power Chord Diminuendo duration reduced to 3 seconds from 4.
Self and allied bonus resistances reduced to 6 / 7 / 8 / 9 / 10 from 8 / 11 / 14 / 17 / 20.
Aura bonus resistances aura changed to 6 / 7 / 8 / 9 / 10 from 3 / 6 / 9 / 12 / 15.
V3.02
General
New splash artwork for Sona OriginalCircle Original Sona.
REMOVED: Power Chord Power Chord being consumed when attacking wards.
V1.0.0.152
Stats
Movement speed increased to 330 from 305.
V1.0.0.150
Stats
Health reduced to 410 from 450.
Armor reduced to 9 from 11.
V1.0.0.148
Ability tooltips updated
V1.0.0.143
General
All auras persistence durations reduced to 1 from 2.
Global cooldown reduced to 0.5 seconds from 2.
Stats
Basic attack and Power Chord Power Chord projectile speeds increased to 2000 from 1500.
Power Chord Power Chord
NEW EFFECT: Resets Sona's basic attack timer.
Crescendo Crescendo
Damage changed to instant from over time.
NEW EFFECT: Damage is not removed by Cleanse Cleanse or Quicksilver Sash item Quicksilver Sash.
V1.0.0.142
Hymn of Valor Hymn of Valor
Cost changed to 45 / 50 / 55 / 60 / 65 from 65 at all ranks.
Champion prioritization range slightly increased to match her attack range.
V1.0.0.136
Power Chord Power Chord
Base damage increased to 8 + (10 × level) from (10 × level).
V1.0.0.134
Power Chord Power Chord
Damage changed to (10 × level) from 14 + (9 × level).
Hymn of Valor Hymn of Valor
Bonus AD and AP reduced to 4 / 8 / 12 / 16 / 20 from 8 / 11 / 14 / 17 / 20.
Aria of Perseverance Aria of Perseverance
Bonus resistances reduced to 3 / 6 / 9 / 12 / 15 from 7 / 9 / 11 / 13 / 15.
Song of Celerity Song of Celerity
Bonus movement speed reduced to 4 / 8 / 12 / 16 / 20% from 8 / 11 / 14 / 17 / 20.
V1.0.0.133
Power Chord Power Chord
Fixed a bug where it did not trigger while taunted or silenced.
V1.0.0.132
General
Splash artwork for Sona SilentNightCircle Silent Night Sona updated to the Chinese art.
Guqin resized to match the other skins.
V1.0.0.131
No longer automatically acquires attack targets when idle while Power Chord Power Chord is active.
V1.0.0.129
Aria of Perseverance Aria of Perseverance
Cost changed to 60 / 65 / 70 / 75 / 80 from 65 at all ranks.
Bonus resistances reduced to 7 / 9 / 11 / 13 / 15 from 8 / 11 / 14 / 17 / 20.
V1.0.0.125
Aria of Perseverance Aria of Perseverance
Heal changed to 40 / 60 / 80 / 100 / 120 from 25 / 50 / 75 / 100 / 125.
V1.0.0.124
Lockout time while casting Sona's songs reduced to make them more responsive.
Aria of Perseverance Aria of Perseverance
Heal reduced to 25 / 50 / 75 / 100 / 125 from 35 / 70 / 105 / 140 / 175.
AP ratio reduced to (+25% AP) from (+35% AP).
NEW EFFECT: Grants passive aura bonus to both her heal target and herself again as an extra bonus for 3 seconds.
BUG FIX: Hymn of Valor Hymn of Valor and Aria of Perseverance Aria of Perseverance caused Sona to deal 20% reduced damage.
V1.0.0.123
Ability tooltips updated.
V1.0.0.120
Fixed a bug where shields and Ignite Ignite could sometimes cause her spell sounds to get cut off early.
V1.0.0.118
Sona will no longer automatically acquire attack targets when Power Chord Power Chord is charged.
V1.0.0.116
Power Chord Power Chord
Aria of Perseverance Diminuendo duration increased to 4 seconds from 3.
Song of Celerity Tempo slow increased to 40% from 35.
Hymn of Valor Hymn of Valor
Bonus AD and AP increased to 8 / 11 / 14 / 17 / 20 from 6 / 8 / 10 / 12 / 14.
V1.0.0.115
General
Stances cost reduced to 65 from 75.
Power Chord Power Chord
Fixed a bug where Aria of Perseverance Diminuendo was reducing true damage.
V1.0.0.113
Power Chord Power Chord
Base damage reduced to 14 + (9 × level) from 24 + (12 × level).
NEW EFFECT: Has a bonus effect based on Sona's last song played.
Hymn of Valor Hymn of Valor
Base damage reduced to 50 / 100 / 150 / 200 / 250 from 60 / 110 / 160 / 210 / 260.
AP ratio increased to (+70% AP) from (+50% AP).
Cost changed to 75 at all ranks from 65 / 70 / 75 / 80 / 85.
Power Chord NEW EFFECT: Staccato.
Deals double Power Chord Power Chord damage.
Aria of Perseverance Aria of Perseverance
Heal increased to 35 / 70 / 105 / 140 / 175 from 30 / 55 / 80 / 105 / 130.
AP ratio reduced to (+35% AP) from (+50% AP).
Cost changed to 75 at all ranks from 65 / 70 / 75 / 80 / 85.
Power Chord NEW EFFECT: Diminuendo.
The target deals 20% reduced damage for 3 seconds.
Song of Celerity Song of Celerity
Cost changed to 75 at all ranks from 65 / 70 / 75 / 80 / 85.
Power Chord NEW EFFECT: Tempo.
Slows the target by 25% for 2 seconds.
Crescendo Crescendo
Cooldown decreased to 140 / 120 / 100 seconds from 170 / 150 / 130.
AP ratio increased to (+80% AP) from (+70% AP).
V1.0.0.106
Hymn of Valor Hymn of Valor
Base damage reduced to 60 / 110 / 160 / 210 / 260 from 70 / 120 / 170 / 220 / 270.
AP ratio reduced to (+50% AP) from (+60% AP).
Aria of Perseverance Aria of Perseverance
Heal reduced to 30 / 55 / 80 / 105 / 130 from 40 / 65 / 90 / 115 / 140.
Song of Celerity Song of Celerity
Bonus movement speed reduced to 6 / 8 / 10 / 12 / 14% from 8 / 10 / 12 / 14 / 16.
V1.0.0.105
General
All auras persistence durations reduced to 2 seconds from 3.
All auras buff durations for allies that exit range reduced to 0.25 seconds from 1.
Hymn of Valor Hymn of Valor
Bonus AD and AP reduced to 6 / 8 / 10 / 12 / 14 from 8 / 11 / 14 / 17 / 20.
Mana cost increased to 65 / 70 / 75 / 80 / 85 from 55 / 60 / 65 / 70 / 75.
Song of Celerity Song of Celerity
Bonus movement speed reduced to 8 / 10 / 12 / 14 / 16% from 8 / 11 / 14 / 17 / 20.
Mana cost increased to 65 / 70 / 75 / 80 / 85 from 55 / 60 / 65 / 70 / 75.
Aria of Perseverance Aria of Perseverance
Mana cost increased to 65 / 70 / 75 / 80 / 85 from 55 / 60 / 65 / 70 / 75.
Crescendo Crescendo
Range reduced to 1000 from 1100.
V1.0.0.104
Crescendo Crescendo
Cooldown increased to 170 / 150 / 130 seconds from 160 / 140 / 120.
Fixed a bug where Song of Celerity Song of Celerity was granting more movement speed than intended.
V1.0.0.101 - Added
Power Chord Power Chord (Innate)
INNATE: After 3 spell casts, Sona's next attack will deal 100 − 440 (based on level) magic damage, and reduce the damage the target deals by 30% for 3 seconds. Additionally, Sona's Auras persist for 3 seconds after deactivating.
Hymn of Valor Hymn of Valor (Q)
ACTIVE: Sona fires bolts of sound, dealing 70 / 120 / 170 / 220 / 270 (+60% AP) magic damage to the nearest two enemies (prioritizes champions).
AURA: Sona plays the Hymn of Valor, increasing nearby allied champions Attack Damage and Ability Power by 8 / 12 / 16 / 20 / 24.
Aria of Perseverance Aria of Perseverance (W)
ACTIVE: Sona sends out healing melodies, healing Sona and the most wounded nearby allied champion by 50 / 75 / 100 / 125 / 150 (+60% AP).
AURA: Sona plays the Aria of Perseverance, increasing nearby allied champions Armor and Magic Resist by 8 / 12 / 16 / 20 / 24.
Song of Celerity Song of Discord (E)
ACTIVE: Sona energizes nearby allies, granting them 14 / 18 / 22 / 26 / 30% Movement speed icon bonus movement speed for 1.5 seconds.
AURA: Sona plays the Song of Discord, granting nearby allied champions 14 / 18 / 22 / 26 / 30 Movement speed icon bonus movement speed.
Crescendo Crescendo (R)
ACTIVE: Sona plays her ultimate chord, forcing enemy champions in a line in front of her to dance, taking 150 / 250 / 350 (+70% AP) magic damage over 2.5 seconds.