RK-64 Buro [A r] [k eI] [s I k s] [f O r] [b u 4 O] is the UTAU voice library managed by ROBORACCOON inc.

Their voice provider is a native Spanish speaker, as well as fluent in English; Making Buro’s primary languages as a voicebank to be Japanese, English and Spanish.

As an UTAU Voice Library, RK-64 Buro has a Standalone 2/3-pitch Voicebank in the Baritone range, and separate expansions are available to make their voice more versatile.
Each library has it’s own set of extra samples to it, check each voicebank’s readme to learn about them.

Below is a list of the currently available Voice Color Add-Ons (Availability varies per library):

SOFT: A softer, slightly more quiet voice tone, with a looser accent.
HARD: A louder, more firm voice tone, which retains a rather similar accent to its base counterpart.
DARK: A soft, slightly lower in tone voice with a smoother accent.
VIVID: A cheery voice that’s higher in tone, resides slightly lower than HARD in terms of volume
WHISPER: A voice that’s quieter than SOFT, though it keeps its tone similar.
SWEET: A voice that’s quiet, much like WHISPER, but sings in the tone of VIVID.
SHOUT: A louder voice, similar to HARD, but with a more prominent accent inspired by “vkei” vocals
SHOCK: A guttural death growl-like voice. Works best in Bass ranges.
FALSETTO: A falsetto pitch that is manually activated. Recorded at A#4.
GHOSTLY: A truly whispered voice. Works best with tn_fnds.
AIRY: A strained and breathy voice. In R2, Starting CVs have a vocal fry quality.
HARSH: A loud voice with a lightly nasal tone. In R2, Starting CVs have a growl.

Sample audios of these voice colors can be found at ROBORACCOON Inc.’s SoundCloud profile.