Bard-barian Builds

[Draco4472]

I got my younger brother interested in D&D some time ago, and have ran a couple games for him and some friends of mine. So far he's only played a barbarian (whose goal up until this point has been to hit something so hard it explodes). Now he's heard great things about bards and is interested in playing one of those, but has also grown fond of his barbarian. When I mentioned a hypothetical Bardbarian with a greataxe that doubles as a lute, he was all behind the idea. Since he's still new to the game, he's looking to me to optimize his character, or at least make recommendations on what works best.

Having never played a Bard nor a Bard/Barbarian, I'm unsure of how to go about this, and so I'm asking for any optimized builds for this multiclass.

On a side note, given his character wants to hit things so hard they explode, I'm considering mentioning a 2 level dip in Paladin to him for Divine Smite (which is as close to 'my axe makes things explode' as I can get). Thoughts on a 'Bard-bar-adin'?

EDIT: His PC's Stats are as followed. I used the standard array when helping him make his PC as, again, he is new to the game. Str: 16, Dex: 14, Con: 15, Int: 9, Wis: 11, Cha: 13. Race is standard Human.

[Specter]

The best thing bardbarians can do is grapple or shove, due to Expertise in Athletics and advantage from Rage. So Shield Master comes to mind. Also, since he'll have advantage on DEX saves, he'll be able to nullify area damage very often. I think this is the best way to go.

The heart of the question is whether to go Barbarian 5/Lore Bard or Barbarian 4/Valor Bard. Personally I prefer the latter because it's more suited thematically for a Barbarian. Good splits are 4 Barb/16 VB and Barb 8/LB 12. You want as many ASI's as you can get.

For Barbarian, both Bear and Wolf work just fine; either be the unwielding champion, or the tactical leader.

When it comes to spells, it's important to focus on those with a non-concentration duration (like Mirror Image and Fire Shield), so they can be used along with rage. But I'm guessing spellcasting will be more utility and healing-focused.

[joaber]

I would go lore bard, valor don't add much to a barbarian multiclass, he already have prof with weapons and shields and extra attack.
Lore bard could give him cutting word, so no one could get away from his grapple, but this would be better with high Cha.
Problem in that build is he can't cast or concentrate while in rage, and with low Cha, he need to focus in spells that don't have saves. Lore bard 6 could bring some good options, like armor of agathys, that is really nice with resistence to damage.

[Ophialor]

I would just drop the barbarian altogether... rage and concentration just don't work well together, and the bard list is mostly concentration spells. You'd do better with fighter, pally or even cleric.