Minecraft wiki entry for playsound, associated text: Specifies the pitch of the sound. If not specified, defaults to 1.
Must be a Single-precision floating-point format number. In Java Edition, it must be between 0.0 and 2.0 (inclusive).
In Java Edition, values less than 0.5 are equivalent to 0.5. Values lower than 1 lower the pitch and increase the duration; values greater than 1 raise the pitch and reduce the duration. The pitch value is a multiplier applied to the frequency, so if a value from 0.5 to 1 is doubled, the pitch goes an octave higher. (See Note block § Usage for converting other intervals to pitch values, but be aware that 1 isn't F♯ for all sound effects.)
In Bedrock Edition, only values between 0 and 256 work. Values above 256 are equivalent to the default value; values less than or equal to 0 makes the sound inaudible.[more information needed]