A situation occurred where a cheeky Bard spoke afoul one too many times in the presence of some seriously bad hombres, and as a result, he got half his tongue cut out.
Now I'm not familiar with how much having a partial tongue interferes with speaking, but the table argued that he can say some words with great difficulty.
This thread in particular that goes into the details of casting while underwater concludes that you ultimately can, RAW, cast spells underwater, arguing that the sound produced in your larynx is the same sound produced above water, it just becomes garbled as soon as it hits the water.
Moreover, here's what the PHB says about verbal components:
Most spells require the chanting of mystic words. The words themselves aren’t the source of the spell’s power; rather, the particular combination of sounds, with specific pitch and resonance, sets the threads of magic in motion. Thus, a character who is gagged or in an area of silence, such as one created by the silence spell, can’t cast a spell with a verbal component.
So, we need Mystic Words to be spoken. Does pronunciation affect the casting? How much does intelligibility affect the casting? To extrapolate this, do characters with poor accents suffer in a similar regard if our bard cannot cast verbally due to his terrible pronunciation? The thread above dictated that you don't even need to be understood, simply the correct pitch and resonance needs to be met.
Is the bard doomed or can he mumble his way around the battlefield?
Best Answer
Ask your DM
Unfortunately, there really isn't any RAW for how to handle damaged tongues or even being mute. For the most part, and except for an optional damage rule from the DMG, there really aren't RAW mechanics for PCs losing body parts.
And all of this is dependent on how a DM defines the disability.
If they rule that the character is mute, then they are effectively under the Silence spell. If it is somewhere in between mute and full speech, then they'll have to make a ruling on how that will affect the Bard.
Workarounds
If the DM does rule that the character is either a mute or their speech is damaged enough to affect Verbal components, then there are some remaining options.
Cast Regenerate
This is the most obvious solution. Either have a party member or a hired caster cast Regenerate to regrow that tongue. Once regrown, all is back to normal.
Dip Sorcerer for Subtle Spell
If regenerating is not an option and they'd like to be able to cast some verbal component spells, then dipping into sorcerer would allow this. However, the downside is needing to forego bard progression in order to do this and this will require a minimum 3 level dip in order to get the Subtle Spell metamagic that would allow bypassing of verbal components.
Simply avoid verbal component spells
This is by far the least attractive option because there are only a few spells under the entire bard list that don't require a verbal component.
This happened at my table, here's what we did and how the players reacted:
In one game I was playing in, this happened to one of the PCs. Our DM ruled that they could not cast a spell with verbal components and they suffered this until we were able to regenerate their tongue.
From a player perspective, the 'maiming' of a PC was awful. It was awful when/why it happened and it was awful for them to have to deal with it for a day until our other cleric could prepare Regenerate. If you are the DM (or anyone reading who is a DM), I would be very wary about mutilating your players and giving them negative mechanical affects. It removes a lot of fun and adds a lot of table issues that can otherwise be avoided.