So I have been converting my parties characters from 1e to 2e and one of those was a skald, which I built as a barbarian with the bard dedication and it has been going well however on a glance through the spell rules again i noticed spells get the concentration trait from verbal components, something every bardic composition has. Is it unbalanced to ignore that incompatibility so he can use his composition cantrips and composition focus spells or would this be overreaching?
I'd say overreaching, since a big design choice is that spellcasting + rage is a big no-no without significant investment and drawback for doing so. Even if you decide to utilize an instrument in place of speaking, it won't lose the Concentrate trait. What you need are abilities that let you circumvent either Verbal components, Concentrate traits, or apply the Rage traits to things that won't normally let you do so in a Rage.
That being said, the Moment of Clarity feat for Barbarians would let you cast spells during a rage at the cost of an action, and you'd really only want to rage in pinches, since you get bonus damage and temporary HP at the cost of AC, so the big question is "How often do I need to Rage and cast Bard Spells at the same time?" A really skilled tactical player can reduce or eliminate these interactions and you'll make for a fairly versatile character, able to buff when needed. Feats like Lingering Composition will let your songs last for a bit, letting you go beat faces for a couple rounds before you need to utilize Moment of Clarity and repeat the process (shouldn't be necessary except for boss fights). Haste will be your friend here (can reliably acquire it with Basic Spellcasting as you gain in levels), since you can spend 2 actions to reapply song (1 for Moment of Clarity, 1 free action for Lingering, 1 extra action for Inspire Courage), one action to get into position (if an enemy moved), and your bonus action to attack said enemy (or vice-versa, or even attack twice if you don't need to move). You won't be able to do cool abilities that require more than 1 action with this, but you can still function pretty well without them as far as participating in combat. Plus, if you have other allies who are beatsticks like yourself, they will appreciate your buffs quite a bit, and spellcasters won't have to waste (as many) spell slots for buffs as well.
If you really want to spread the multiclass theme, there is the Silent Spell feat from Wizards that lets you substitute Verbal components for Somatic or Material components.
If you're willing to homebrew it, I'd simply make Skald a dedication feat variant to the Bard, requiring either the Rage class feature or the Composition cantrips feature, as well as a certain amount of Charisma and Strength (14 in both I imagine), as well as being trained in 2 of either Athletics, Intimidation, or Perform. The feat will grant Inspire Courage and one cantrip from the Bard spell list, as well as trained Spell DC with the ability to cast spells if you don't have them, or trained in Medium armor and all Martial weapons, and a once per day Rage if you don't have that. As for feat chains, probably allow Basic and Expert spellcasting feats (no Master spellcasting), a permanent Rage feat, a basic Bard or Barbarian class feat with options to select only advanced Rage or Composition feats, a feat that applies the Rage trait to spells gained from your Skald dedication or Bard class, as well as maybe a feat that lets you combine both a handheld instrument and a weapon simultaneously, letting you use said item as either, and counts as either item for all intents and purposes.
But all of that is only if you're the GM willing to homebrew stuff. YMMV of course, and I hope I gave you some good ideas as to make this a reality!
Well remember his pf1 build was a skald, song + rage was the entire playstyle, before I noticed the error he had been using his inspire courage composition cantrip basically constantly to keep his war chant going both in and out of rage
Even in PF1, the Skald had special abilities that let them cast their spells while in a Rage, and only spells from their class, not other classes (which required a separate feat if I remember), and Bloodragers (Sorcerer + Barbarian) functioned this way too, requiring special class features and additional feats to work the way it's supposed to.
Plus, I was referring more to the PF2 design goals than the PF1 design goals.
Being able to use use concentration components while raging seems totally within the range of an instinct. Perhaps having a custom instinct with the instinct ability that they can perform verbal actions while raging.
Skald Instinct
Anathema
Interrupting the telling of a story is anathema
Instinct Ability
You can perform actions with the auditory and verbal trait while raging.
Specialization ability
Increase the additional damage from Rage from 2 to 6. If
you have greater weapon specialization, instead increase
the additional damage from Rage to 12.
Raging Resistance
You gain resistance to sonic and bludgeoning damage