voice-pitch property is used in speech media to specify the baseline pitch of the speaking voice.
More specifically, the CSS specification states that it specifies the "baseline" pitch of the generated speech output, which depends on the used
voice-family instance, and varies across speech synthesis processors (it approximately corresponds to the average pitch of the output).
- This value represents the frequency of the baseline pitch. If the
absolutekeyword is present, this is an absolute frequency (it's not an increment or decrement). A common pitch is around
120Hzfor a male voice, and around
210Hzfor a female voice.
- This is an optional keyword that indicates that the specified frequency represents an absolute value (i.e. it's not an increment or decrement). If a negative frequency is specified, the computed frequency is zero.
- Specifies a relative change (decrement or increment) to the inherited value. This is specified as a number followed immediately (no space) by
st(semitones unit identifier).
- A sequence of monotonically non-decreasing pitch levels that are implementation and voice specific.
- Positive and negative percentage values are allowed, to represent an increment or decrement (respectively) relative to the inherited value.
In addition, all CSS properties also accept the following CSS-wide keyword values as the sole component of their property value:
- Represents the value specified as the property's initial value.
- Represents the computed value of the property on the element's parent.
- This value acts as either
initial, depending on whether the property is inherited or not. In other words, it sets all properties to their parent value if they are inheritable or to their initial value if not inheritable.
- Initial Value
- Applies To
- All elements.
- CSS Speech Module (W3C Candidate Recommendation 20 March 2012)
For maximum browser compatibility many web developers add browser-specific properties by using extensions such as
-webkit- for Safari, Google Chrome, and Opera (newer versions),
-ms- for Internet Explorer,
-moz- for Firefox,
-o- for older versions of Opera etc. As with any CSS property, if a browser doesn't support a proprietary extension, it will simply ignore it.
This practice is not recommended by the W3C, however in many cases, the only way you can test a property is to include the CSS extension that is compatible with your browser.
The major browser manufacturers generally strive to adhere to the W3C specifications, and when they support a non-prefixed property, they typically remove the prefixed version. Also, W3C advises vendors to remove their prefixes for properties that reach Candidate Recommendation status.
Many developers use Autoprefixer, which is a postprocessor for CSS. Autoprefixer automatically adds vendor prefixes to your CSS so that you don't need to. It also removes old, unnecessary prefixes from your CSS.
You can also use Autoprefixer with preprocessors such as Less and Sass.