I am designing a guitar pedal using OpAmps, and i need to feed them with +6V and -6V (beucase the musical signal is senoidal centered in 0V). I need to use a 12V DC PSU for the pedal, and i need to convert to positive and negative voltage. If possible it would be better if it was +12V and -12V but if its not possible i can work with +-6V. I also need this to be reasonably simple and cheap. Thanks!
I'm assuming you mean +/- 6 V from the body of your question, rather than +/- 5 V from the title.
There are a number of ways to achieve this, depending on both your budget, and power budget. You probably don't need a huge amount of power for this application, so the easiest route is probably TI's TLE2426 rail splitter IC.
A second option is something like the following, the Virtual Ground node isn't really 0 V, it's +6 above the GND node, but you treat it as your 'virtual ground' and the actual ground node becomes -6 V.
If you need to sink and source more current than the opamp can supply you can add a buffer (such as TI's BUF 634) which is an expensive option, or put a push pull stage within the feedback loop.
You could also AC couple and bias your signal to +6 V so you don't need to worry about the negative supply.
Ground is an illusion. We choose a node and decide we're going to call it 0V, and give it the magical name ground. If you create a reference of 6V from your 12V supply, and call it ground, your 12V supply just became +/-6V.
Of course, ground is also assumed to be low impedance, so you'll have trouble if you create it using a 100K voltage divider and then try to use it as a current return. Because of that, we generally call it Vref, and thus remember to take into account its current limitations relative to the supply.
If there's a DC offset between Vref and your I/O, capacitors will resolve it nicely.