Alter/Ego

Alter/Ego (アルター・エゴ) is a free real-time vocal synthesizer software which was created by Plogue.
About.
Alter/Ego is a text-to-speech synthesizer which aims to create more modern vocals, working to post 1990s research. It was offered as a free plug-in and is used for music making to produce singing vocals. It operates in a similar manner to Chipspeech. Vocals are clean-cut though robotic sounding and the software is ideal for vocal experimentation. It is capable of running different speech engines.
There are currently only 2 released vocals for the software. The released vocals are purchased separately. The vocals come as files that need to be extracted as they lack installers. Over time Plogue have received many vocal requests from individuals since the release of the software, however they are limited by their small development team and being busy.
In January 2016 it was announced that there were 6 new vocals in production. No more vocals are due after Leora and Marie Orks final two vocal updates. Plogue have since moved on to other adaptations of the engine. One such adaptation is the ability for the engine to detect Microsoft text-to-speech voices and load them into the engine. UTAU has also been experimented with. Plogue noted that the engine was designed to have user made vocal support from the beginning, though this was yet to be implemented due to a lack of support for this.
In 2017 the production of new voicebanks ceased with Marie Ork "Clear" and Leora having been confirmed the last voicebanks being produced for the software. The cease of new voicebanks came in the wake of a scandal with the creator of voicebanks "Vera" and "Nata". Though the engine has been updated since 2017, since it is identical to the Chipspeech engine, the overall development of Alter/ego has ceased.
Reception.
As noted by BPB, Alter/Ego is praised for being a powerful tool by standards of free software. It, however, has a steep learning curve, though highlighted how easy it was to get the synthesizer to sing lyrics, calling the product "fun" to work with overall. Later in December that year, the software was awarded second place in their top 50 free instruments list.
Computer Music magazine also covered the synthesizer in their December 2015 issue.