Free text-to-speech (TTS) or speech synthesizers
Your computer almost certainly comes with at least one synthesizer. Later versions of Windows have better voices and more of them. Below are some free options that all support SAPI5 - that is, they will work with most software on a Microsoft Windows machine. All will work with the Thunder and NVDA free screenreaders.
Universities and public bodies regularly produce new speech synthesizers from research projects and attempts to support their language or accent. These either disappear from the web after a year or two or get brought up and commercialised by a new or existing speech synthesis company. eSpeak is the exception: it's been around for a decade at least. But any of the other links below may be broken or no longer provide the voice described.
Microsoft Windows has shipped with a speech synthesizer since Windows 2000 - Microsoft Sam until Microsoft Vista, other voices since then. English and Chinese were usually freely available. Windows 8 added many speech synthesizers available for lots of languages. You simply install the "Language Pack" from Control Panel and the voice will appear.
Confusingly, Windows 10 also has many voices that are Windows Runtime voices or Mobile voices, not the SAPI5 voices that will work in your software. See Microsoft Speech on the Blog for more details. None of the below are these Windows Runtime voices.
All these SAPI5 voices can be expected to be found on Windows 8.1 and 10, either because (1) I've installed a language pack and found them or (2) they are on the Microsoft website, though incorrectly labeled.
- Windows 8
- Korean Heami
- US English David
- UK English Hazel
- US English Zira
- Spanish Helena
- French Hortense
- German Hedda
- Japanese Haruka
- Chinese (simplified) Hanhan and Huihui
- Windows 8.1 and 10 - all the above plus:
- Mexican Spanish Sabina
- Indian English Heera
- Chinese (traditional) Tracy
- Italian Elsa
- Polish Paulina
- Portuguese Maria (possibly Brazilian)
- Russian Irina
eSpeak is an open-source (GPL V3) TTS system. There's a SAPI5 DLL, and commandline options. It's developed by Jonathan Duddington. It's probably the most common speech synthesizer in open-source systems at the time of writing. It sounds like a "traditional" speech synthesizer - quite robotic - but this means it's exceptionally clear, high-performance and easy to add language support to it. I know many blind people who use it exclusively in preference to the commercial "human-sounding" voices.
- Open-source eSpeak voices - "usable" and "provisional"
- Voice variants for the voices - male and female, and 5 variants of each, and "croak" and "whisper".
- Non-open-source MBROLA voice support. There is a wide range of these, and they are good, but the licence is not GPL: you have permission to redistribute for non-commercial free programs, and you must use the MBROLA program itself to generate the speech. I'm going to assume that the eSpeak DLL calls the MBROLA engine to be in line with the licence. I notice that you have to get the MBROLA voices separately from the eSpeak install.
On Windows, you can install eSpeak then run "C:\Program Files (x86)\eSpeak\command_line\espeak.exe". The commandline options:
- --voices Show all the voices
- -vXX Use voice XX, e.g. "-vaf" is "use the af voice".
- -vXX+YY Use variant YY, e.g. "-vaf+f2" is "use the af voice with the female variant 2". The variants are:
- None (male voice)
- +m1, +m2, +m3, +m4, +m5 (male variants)
- +f (female voice)
- +f1, +f2, +f3, +f4, +f5 (female variants)
- +whisper (male whisper)
Asharir - Hindi, Tamil, Kannada and Telugu
These were free SAPI5 text-to-speech voices from Asharir in India. However, they've disappeared from the Internet, so until someone complains a download link follows. They supported Hindi, English, Tamil, Kannada, and Telugu, though I can't vouch for them.
- Asharir SAPI5 Setup Installer file.
- Free male and female Welsh synthesizer voices from Ivona. Ivona is a big commercial speech synthesis company, and the Welsh Assembly (the devolved Welsh government within the UK) appears to have paid them to create these two voices for Welsh.
- Free Maltese voice. Again, this looks like a voice paid for by the Maltese government.