"Continuous" Bardic Inspiration

Question

The bard's Bardic Inspiration feature states:

You can inspire others through stirring words or music. To do so, you use a bonus action on your turn to choose one creature other than yourself within 60 feet of you who can hear you. That creature gains one Bardic Inspiration die, a d6.

Once within the next 10 minutes, the creature can roll the die and add the number rolled to one ability check, attack roll, or saving throw it makes.

This basically plays out to be "You can do it!" or "Break a leg!", or just playing their lute to build suspense, to affect one thing at a time.

However, I was thinking about the possibility of changing this up for a more "constant" variation. A smaller pay off (+2, for example) for the entire period, much like listening to your favorite song when doing something challenging; Eye of the Tiger or Danger Zone during a fight, Stayin' Alive while doing a heal or revive check, or just your favorite song to get you in the zone, and your blood pumping.

Additionally, the original time frame is "in the next 10 minutes", which means any time within the next 60 rounds; so a compromise of a constant +2 over say, 1-3 minutes (i.e. the length of your "inpirational boom-box music") would not only fit combat more effectively, but also be more evenly balanced in bonus:duration ratio.

So; would a constant bonus of +2 over a shorter duration (1 minute) be balanced?

Answer 1

Unbalanced and Unconventional

Assuming the Bard still has the same number of Bardic Inspirations per rest this is a much stronger homebrew, and balance isn't the only issue.

Balance Math

For this example, let's take a level 3 Bard with a Charisma of 16. By RAW they have three d6 inspiration dice per long rest. At an average of 3.5 per die, that is a total of 10.5 increase per long rest.

Your variant changes the d6 to a flat +2 benefit, this means for any given roll it will, on average, be less of a benefit than the RAW method. However, by granting a +2 to all rolls for a duration of 1 minute per usage, the total benefit is much higher.

Assuming an average combat length of 3 rounds, any target you use this on is likely to make 3 attack rolls and 1 saving throw per combat (this is conservative). +2 per roll, 4 rolls per combat, 3 combats per day, adds up to a total benefit of +24 per long rest. That is over double the benefit of the RAW method.

The gap only gets wider as you level, at higher levels there are more rolls per round and therefore the constant benefit is even greater.

'But wait!' you say 'this variation doesn't let you choose the important rolls'. Correct, it doesn't, it applies to all of them so you never have to choose if it is more important to use it on this attack, or keep it for your next save. This is power-positive and is unbalanced.

Static Bonuses

It is very rare for a feature to grant a static bonus in 5th edition. A bonus equal to an ability score (e.g. Paladin's Auras), advantage, or an additional dice (e.g. RAW Bardic Inspiration) are far more common. This is part of the design of 5th edition and I usually advise homebrewers to stick within existing examples unless they really know what they are doing.

Complicates Other Features

It is unclear how this would interact with the other uses for Bardic Inspiration, Features like cutting words use Bardic Inspiration dice in a particular way. Would this homebrew rule also apply to the other uses?

It's been this way before

The system you are describing is very close to what exists in Pathfinder 1e and 3.5e D&D. The Bard would spend an action to begin Bardic Inspiration and then could maintain it for free, up to a certain number of rounds per day. While active it provided a static 'morale bonus' to allies within 30ft. This bonus increased as you leveled. There were other were other ways it could be used but they are less relevant.

If you are set on changing this, maybe look into how it worked before and consider how that could be adapted to suit the 5th edition design philosophy.

Answer 2

This gives a low level bard roughly three bless spells for free.

Which means "no, it's not balanced."
Let's compare your idea with the Bless Spell. You want +2 to any roll -attack, save, ability check - for a minute.

Bless

Duration: Concentration, up to 1 minute.
You bless up to three creatures of your choice within range. Whenever a target makes an attack roll or a saving throw before the spell ends, the target can roll a d4 and add the number rolled to the attack roll or saving throw. (Basic Rules, page 89)

Bless is on average +2.5 on saves and attacks, nothing on ability checks. It is a bit stronger than this idea in that it covers three people, but since it requires concentration it can be lost. Your proposal doesn't require concentration.

What you propose is that the bard keep all of her spells and also get a single person bless three times per long rest. After level 5, with Font of Inspiration she gets it 3, 4, or 5 times per short or long rest. With a charisma of 18 the bard would have 12 of these in a standard adventure day that has two short rests. That's a lotta bless equivalents.

Font of Inspiration

Beginning when you reach 5th level, you regain all of your expended uses of Bardic Inspiration when you finish a short or long rest. (PHB, Bard)

Inspiration: gives +(Something) once.
In a three to five round combat, your mod gives +(Something) three to five times. (@linkassassin also covers this). Granted, with three allies and a full three round fight, bless give 9 (+2.5)s to either a save or an attack, but nothing to an ability check, and it burns a spell slot.

Since inspiration does not require concentration, you can spread this benefit out to more party members than a bless spell can and it recharges on a short rest at level 5 and beyond. At higher levels, you'd be sacrificing a bit more potential plus as the dice go up if you kept the benefit to +2 throughout.

Inspiration Absurdum

Just in case you had the idea to increase the + as the bardic inspiration die increases with tier (average round down minus 1, which is how 2 relates to the d6 (3.5-1 round down = 2) this could get quite unbalanced when Inspiration dice is d10 or d12; so if you do keep it, leaving it at a flat +2 is the better idea.
(For completeness' sake: at level 5 that would be a +3, and level 10 +4 and at level 15 a +5; flat bonuses of +4 and +5 don't fit into this edition; the notable exceptions are +5 Initiative ~ Alert feat, and +5 Passiver Perception/Investigation ~ Observant feat).

Answer 3

It isn't detailed enough

A smaller pay off (+2, for example) for the entire period

constant +2 over say, 1-3 minutes

a constant bonus of +2 over a shorter duration (1 minute)

This doesn't clearly describe what the +2 would apply to. All ongoing rolls eligible for Bardic Inspiration? One kind of roll? Can I have +2 to my damage rolls? Does it affect passive checks? Does it scale with levels?
All of these question will arise in an actual gameplay. At the very least, you should write a complete description like other class features have (take the Bardic Inspiration feature for example).

It does not solve any real gameplay issue

There is no reason to throw out a default rule and introduce a new one "just because" without any real issue to be solved as the result.

Rules have costs. When you implement a new rule, you have to work it out, you have to write it down and edit it for clarity, you have to present it to the table and ensure everyone’s understanding of the rule, and then you have to devote game time to testing and enforcing it.

All games, by necessity, skip over some of the details of real life; this is known as abstraction. The choice of abstraction is a very important design consideration for a game — and never a trivial one. There are always trade-offs.

It is not balanced

By "balanced" I mean two things:

• Balanced means "is on par with other game features". Both linksassin's answer and KorvinStarmast's answer show how this new Bardic Inspiration is superior comparing to the default one, along with the Bless spell.
• Balanced means playtested. No one can predict all the issues possible just by means of theorycrafting. Regardless of what we say here, you still have to test this rule in a real game in order to make any boldface statements.

Ask the players what they think about this idea

5e already has the rule for representing bolstering the morale, it's called Bardic Inspiration. It is well-known to players who read PHB. A new rule has costs for players as well. Ask your players, what do they think about this similar but different rule that does nearly the same thing. There is a chance they will be excited about it, they will say "sounds interesting, let's try this". If they won't though, well, probably it isn't such a good idea.