eCantorix2 is a singing voice synthesizer based on Jonathan Duddington's eSpeak multilingual formant synthesizer and Masanori Morise's WORLD Vocoder Library. It also includes QTau, a piano roll editor written using QT that is similar to UTAU and the VOCALOID Editor. QTau uses the JACK Audio Connection Kit allowing the user to "ReWire" QTau to other DAWs such as Ardour. QTau is Logiciel Libre designed to replace Cadencii, of which an old version is included in the repositories of Debian GNU/Linux and its derivates such as Ubuntu and Trisquel. The latest version of Cadencii only runs on proprietary operating systems and is unlikely to be ported. Like Cadencii, QTau supports multiple synthesizer plugins such as MBRØLOID or UTAU-Synth that provide a more natural sound than pure eSpeak.
Development versions of QTau and its dependencies can be found on IsengaaraP's Not A Bug. Precompiled binares for Trisquel 7 and Ubuntu 14.04 are available in the Ongakunix repositories. Ongakunix also contains other software that a Libre Desktop Music Producer needs, such as Ardour4, ZynAddSubFX, the Non-Session Manager and many more.