Piapro Studio is a software synthesizer created by Crypton Future Media, Inc.
Piapro Studio was created to allow the developers to expand their VOCALOID characters in new directions that VOCALOID limited within its software. It was originally sold as an alternative to supplying the full VOCALOID software and was first released with KAITO and the "KAITO V3" software. The first few versions had a form of the VOCALOID API at its core synthesising process.
As it had the VOCALOID API eventually it was able to open up to allow all other VOCALOID from VOCALOID2, VOCALOID3 and from Piapro Stuio2 onwards, VOCALOID4 vocals to be loaded. However, originally it was only made for Crypton Future Media Vocaloids.