Is this very rare or legendary? Can't decide

Orb of Hymns

Wondrous Item, Very Rare (Requires Attunement by a Spellcaster)

A smoky crystal sphere the size of an apple, with threads of golden light snaking within. When used, it resonates with a distant, ethereal choir. Sages claim these orbs were forged by a draconic celestial entity, as a means to speak with its champions. You can use this orb as a spellcasting focus, and it serves as material component for the Scrying spell.

Empowered Summoned Dragon. When you use the spell Summon Dragon using the orb as your spellcasting focus, it doesn’t require Concentration and lasts for an additional hour.

Spells. The orb has 5 charges and regains 1d4 + 1 expended charges daily at dawn. You can cast the spells on the following table from it. You use the same spellcasting ability you use for your spells and still need to provide material components that are consumed. The table indicates how many charges you must expend to cast the spell and you can upcast a spell by spending 1 additional charge per slot level.

Well...

Did you make it for someone who has Summon Dragon as a spell they consistently cast? Because otherwise that's just kind of random.

Otherwise I would label this as Very Rare. Raise Dead is the only thing I could see being a problem, but it still requires components, so it isn't too much of a problem. Giving a wizard cure wounds and things might take away from the healers of the party though, so I would watch for that.

Yes, it's campaign-specific, for a draconic sorcerer. My main concern is if freeing up Concentration for another spell in combat is too much, basically.

The fact that the summon dragon trick isn't one at a time seems like it might be annoying; people don't have that many level 5+ slots, but they likely have more than one.

Is consider what other kinds of shenanigans the character could get up to with the extra concentration. Summon+greater invisibility; summon + haste, etc. They could really buff the dragon. 

But to answer the question, giving 2 concentrations seems like it would push it to legendary. That’s a huge power spike. 

I would have a few extra caveats on this. A good compromise would be that the orb can be used once per day to cast Summon Dragon, so that nobody spends 4 level 5 spell slots to summon 4 dragons!

alternatively, you could replace the extra spells (if it's for a sorcerer, they can do without them) with the ability to cast a second concentration spell.

Rough example (been a while since I wrote a magic item so bear with):

Orb of Hymns

Wondrous item, Legendary, requires attunement from a spellcaster

Whilst attuned to the Orb of Hymns, if you are concentrating on the Summon Dragon spell, and you have advantage on concentration checks you against that spell. Additionally, the spell lasts for an additional hour.

The Orb of Hymns has 5 charges, and recovers 1+d4 charges when you finish a long rest. Whilst you are concentrating on the Summon Dragon Spell, you may expend one or more charges to cast a second concentration spell, expending your spell slots as normal to do so. Doing so does not cause you to lose concentration on the Summon Dragon Spell. The number of charges required to cast a spell this way are equal to the level of the spell slot used to cast it. You are able to concentrate on this spell at the same time as concentrating on Summon Dragon.

Whilst you are concentrating on both spells, you make concentration checks against both of them separately when you take damage.

That should make it more versatile for their needs, but not bloated with extra bits - in my experience, players forget the little details like extra spells etc!

Shoot! I totally missed people can cast Summon Dragon more than once per day, what an idiot! Yeah, the idea is that it can only be used once per day. I added the following:

You can only use this ability once and it recharges every day at dawn.