Sona's Hymn of Valor and Aria of Perseverance are with no doubt auto-targeted spells. Hymn of Valor deals magic damage to up to two enemy units while Aria of Perseverance heals and grants a shield to one allied champion. Why are the two spells auto targeted? Because when the player activates Hymn of Valor they do not have to choose the targets rather it will be selected for them through an algorithm. The same is true for Aria of Perseverance. This latter spell heals an allied champion with the lowest health. Again there is no player input for the selection of targets.
Song of Celerity is different. The first part of the active is a self-buff granting movement speed to Sona only. Then she can tag allies and give them movement speed. In the third basic spell of Sona there is no selection going on. It is a point-blank aura and is therefore not auto-targeted.