Virtual Singers such as Hatsune Miku are very popular in Japan. Before that there was also an MBROLA-based Virtual Singer called Melissa and a multilingual formant synthesizer called Virtual Singer by the French company Myriad. All those Virtual Singers are based on proprietary software, until recently there was no free replacement. In 2011 I discovered that the Music Technology Group had released their Spectral Modeling Synthesis library under the GNU GPL, and I decided to use that one in my own UTAU compatible resampler.