Rocksinger

The Rock Singer learns to use their voice not only to bolster their allies or demoralize their foes, they learn to sing to the earth itself, using the vibrations from their remarkably deep voices (aided by a little magic) to match the natural frequency of the earth around them. This allows Rocksingers to use a handful of earth spells and imbue their party with some of the hearty characteristics of the earth.

Earth Magic

Your link to the earth allows you to learn spells from a list of earth-based spells. When your Spellcasting feature lets you learn a bard cantrip or a bard spell of 1st level or higher, you can choose the new spell from the Earth Spells list or the bard spell list. You must otherwise obey all the restrictions for selecting the spell, and it becomes a bard spell for you.

Earthen Blessing

Also at 3rd level, you learn to impart the heartiness of the earth to others. When an attack roll is made against a creature that has an Bardic Inspiration die from you, it can use its reaction to roll the die and gain temporary hit points equal to the number rolled. These temporary hit points take effect before the attack lands. 

Casting Stones

At 14th level, you learn to weave the deep notes of rocksinging into any spell. When you use your action to cast a bard spell, you can imbue and throw a single Magic Stone without expending your action or bonus action. You can do this up to a number equal to your Charisma modifier (minimum of one). Make a ranged spell attack with a range of 60 feet. On a hit, the target takes bludgeoning damage equal to 1d6 + your spellcasting ability modifier. 

Shifting Earth

At 14th level, you can ask the earth to impede the movement of a creature. As an action, roll a Bardic Inspiration die. Reduce the target's speed by a number of feet equal to 5 times the number you rolled (for example, if you rolled a 4, you would reduce the movement of the target by 20 feet). This reduction in speed lasts until the end of the target's next turn. If you exceed the target's speed by 10 feet or more, the target becomes restrained until the end of their next turn. A restrained creature can use an action to make a DC 13 Strength check. On a success, the creature is no longer restrained.