The Art of Magic and Art of Singing are both arguably the most ancient of arts, so it is not unreasonable for someone to assume that Bards have existed for as long - or even before - written, recorded history have been going on.
However, the truth is much different. Bards are much more recent than one would think. No credible historian can prove the existence of bards further than the foundation of the Kingdoms of Froturn and Dragoc.
The origin of bards can be traced back to the monastic traditions of the High Elves of Froturn. Some clerics composed music whose lyrics were actual Clerical Spells. A special brand of traveling monks, the "singing priests" came into existence, singing healing spells while traveling the land, curing the ill by merely singing.
We don't know how, but this eventually started inspiring the "secular" magicians too, and the tradition of bards quickly spread to Dragoc.
While the "singing priests" gradually faded into obscurity, their secular counterparts - the Bards - slowly rose to prominence.
Even more, the Bards also managed to imbue their spells into instrumental music - they do not even need to necessary open their mouths anymore.
Bards are exclusive to the English-language version of the FRPG.
Bards are a dual-class prestige class, but they are not fixed to two specific classes - they are dual-class between one core Magic-based class (Magician or Druid) and one non-magic class (Thief or Warrior), which means that bards can be users of either Arcane Magic or Nature Magic, depending on the parent class.
Being a Bard grants a bonus of 1 Charisma, and also grants an ability to sing or play Magical Songs - pieces of music (either vocal or instrumental) that act like spells that can be cast. This allows them to use magic even while Silenced.
Bards did not appear in any of the video game adaptations, but are planned to appear in future attempts.