This sounds fairly straightforward. What degree of precision is acceptable between the different events? I'm thinking that a microcontroller is a good solution to this application, but this implies that there will be time delays on the order of perhaps one to ten microseconds. If this time error is trivial, then a microprocessor is perhaps the easiest solution. I like the Atmel AVR series since the parts are inexpensive, you can make your own programmer quite easily, and software for development is all available for free. So, give us your best guess on how accurately the sound pulse should line up with the LED illumination. What frequency do you want the audio sample to be? Would you like a pure tone, or perhaps something more complex?
To get things started, consider using an AVR development board made by Olimex, or Sparkfun or one of the many others supplying such things. They are widely available with many options, and usually less than 30pounds in cost. This gets you started very quickly. While you are at it, these suppliers often sell simple programmer cables that allow download of code from your PC to the board for about 10pound more, so buy that too. Let us know your level of programming skill. If you know the C programming language, then you are well along already. If not, but you know how to program in BASIC there is a good solution there too. Another choice is to go with an Arduino or such platform instead, which is easier to program.
interfacing a micro to turn on and off LEDs is quite simple. for lower power (ie 20mA) LEDs, you can wire each led directly through a resistor to the microcontroller. For higher levels of current, a buffer transistor will be required to give some current gain, one transistor for each bank of LEDs. I prefer using an N channel FET between the LED cathode and ground as these are cheap, very good and reliable. You still need the current limiting resistor in series with the LED too. If you want to run fairly high power LEDs (like 1 watt), then we should use a constant current source or specialty IC designed to drive an LED. So please decide how bright the LED has to be first. I can say that using a black background allows a white LED of only medium power to be visible for a long way.
The microcontroller can easily generate a simple audio tone directly from one of its i/o pins, but an amplifier would be required to drive a speaker. You should also use an op-amp to buffer this audio out to the line output, so we are talking about two amplifiers, one for driving an 8 ohm speaker and an op amp for driving the line.