A synthetic speech calculator is provided which is capable of generating an audible sound signal which can be representative of keyed data, sequences of keyed data (and errors), processed data, the contents of a memory or the contents of a counter. The sound signal can be suppressed under certain specific circumstances or made soft in intensity. A synthetic-speech calculator includes the keyboard consisting of digit keys and function keys, a desired number of registers for storing information entered by the depression of selected ones of the digit keys, a read-only-memory for storing a large number of digital codes as sound quantizing information, counter means for specifying the address of the memory so as to take a specific digital code out of the memory, a digital-to-analog converter for converting the specific digital code taken out of the memory into an audible sound signal, and a loud speaker driven by the audible sound signal and producing an audible sound. There are provided means responsive to combinations of at least two sequentially operated keys of the keyboard for modifying the output condition of the audible sound, for example, volume, speed, etc. The synthetic speech calculator also has a selection key and multi-function keys, such as 7/sin.theta.. If the selection key is depressed followed by actuation of one of the multi-function keys, as audible sound indicative of the second function of the multi-function key is audibly generated, i.e., "sin.theta." is audibly generated. If the selection key is not depressed prior to actuation of the multi-function key, an audibly sound indicative of the first function (7) is audibly generated. Similarly, the calculator will also develop an audible sound indicative of "EQUAL" if the following key sequence is actuated: a.times.b=, where a and b are numerals. The calculator will develop an audible sound indicative of "TWO" if the following key sequence is actuated: a.times.=. An audible sound indicative of "THREE" will be developed if the following key sequence is actuated: a.times.==.