What is the maximum duration on BRD songs? With and without mythic. (Im terrible at math)
Depends on the song. Each +1 to song gives +10% duration. Some songs get more "+1" than other type of songs.
Some songs get those "+1" from slot with no other duration options, some other songs get it in slot with concurrent but lower duration bonuses (feet, legs).
You can further extend the duration of songs by going /NIN or /DNC and offhanding a Kali (5% duration).
The longest duration you can reasonably achieve on a song it should be on Honor March (with Marsyas) or Etudes (with Horn).
Technically Etudes with Marsyas would be 10% longer but also weaker so *** that. (I'm also ignoring stuff like Scherzo, Mazurka, Hymnus etc)
This duration value corresponds to 805,6 seconds. That's 13 minutes and 25,6 seconds.
To achieve this of course you need all duration gear, all +song gear, Kali offhand, Clarion Call up, Soulvoice
DOWN, Marcato up.
Granted that's not particularly realistic either.
I'd remove 20 seconds from the values I posted above and consider that your currently maximum song duration value, which applies only to Etude and Honor March as I mentioned. All other songs should last ~10% less.
Hope I didn't forget or miscalculate anything! Don't have my BRD lua with me atm.
Edit:
Oh I think Carols can reach the same duration values as Etude and Honor March actually.
Madrigals, March and Minuets ~10% less, Minne ~3% less, Mambo ~5% , Ballads ~7% less, most other songs ~20% less duration approx
Edit2:
Stuff I counted for the above calculation:
50% (Carnwenhan), 30% (HQ Neck), 12% (AF3+1 body), 17% (Inyanga+2 legs), 15% (AF1+3 feet), 5% (Gift), 5% (Kali), 40% (Ghorn) or 50% (Marsyas, only for HM).
Then Madrigals, Minuets, March get a +10% in non-concurrent slots to the gear above, whereas Etudes and Carols get a +20%
Minne/Mambo get +20% but in a slot with 17% and 15% existing duration respectively.
Ballad get 10% in a slot with 17%.
The formula for duration is something like:
(((BaseDuration * BonusDuration) + ClarionCall bonus) * 2 ) + MarcatoBonus
ClarionCall bonus is 40 seconds at capped JPs.
The *2 is of course from NiTro.
Marcato Bonus doesn't get multiplied by NiTro but added after, and it doesn't apply if SoulVoice is active.