Fighter specializing in buffing the whole team and beating people into a bulp with the battle horn. 

Melodic Fighter

Starting when you choose this archetype at 3rd level, your fighting stance consists of playing the horn and rocking to the music. This hypnotic movement gives you +1 to your AC if you are not wearing heavy armor.

You also gain profiency in Performance. 

Instrument of War

You gain proficiency in Battlehorn, the weapon-instrument hybrid. Its a two-handed club-like weapon, dealing 1d8 + your Strength modifier bludgeoning damage.

When you attack with a Battlehorn you gain a note or three if the attack is critical. You need three notes to play a melody. As a bonus action on your turn you can play a single melody. Notes last 1 hour after the attack.

You learn 2 melodies once you select this Martial Archetype. You learn more melodies at levels 7, 10, 15 and 18. You can change one melody each time you reach a level in this class.

Brisk melody

Every creature of your choice in 30 feet radius that can hear the melody, gets a movement bonus of 10 feet. This lasts until the end of your next turn.

Brutal melody

Every creature of your choice in 30 feet radius that can hear the melody, gets a bonus to its damage rolls equal to your proficency bonus. This lasts until the end of your next turn.

Distracting melody

Every creature of your choice in 30 feet radius that can hear the melody, gets a disadvantage on their next saving throw. This lasts until the end of your next turn.

Forceful melody

You play a tune of great pressure. Every creature of your choice in 10 feet radius that can hear the sound must make an strength saving throw. On a failed save a creature gets pushed 10 feet away from you.

Sharp melody

Every creature of your choice in 30 feet radius that can hear the melody, are immune to being charmed and frightened. This lasts until the end of your next turn.

Sound wave

You play a thunderous roar. Every creature of your choice in 10 feet radius that can hear the sound must make an constitution saving throw. On a failed take 1d6 plus your charisma modifier thunder damage, and half if it succeeds.

This increases to 2d6 at level 10.

Swaying melody

Every creature of your choice in 30 feet radius that can hear the melody, gets a bonus to its AC equal the half of your charisma modifier, rounded up. This lasts until the end of your next turn.

Vigorous melody

Every creature of your choice in 30 feet radius that can hear the melody, gets temporary hit points equal to your proficiency bonus. This lasts until the end of your next turn.

Loud and Clear

Upon reaching 7th level, the range and duration of all your non-damaging melodies are doubled. 

Consert player

When you reach 7th level, you can play as many melodies in one bonus action as you have banked notes in sets of three.

Catchy tune

When reaching the 10th level, you can start to hum one of your non-harmful melodies. That melody activates every turn passively and only for you. You can choose a melody at the start of the combat and change it as a bonus action.

Powerchord

At 15th level, you need one less notes to play a melody.

Battlechant

Once reaching the 18th level, instead of humming, you sing the Catchy Tune. Now it affects creatures of your choice in 30 feet that can hear it.