Audio signal "Flasher"

[Pacchio]

Hello everybody.
I must ask you a question. I would create a "audio signal flasher" in this way:
an integrated 555 generates a square wave (which I manage with potentiometer) which shall be, for example, from 0 to 10 V (as here for example http://www.falstad.com/circuit/e-555square.html).
The square wave drives a relay which closes when the signal is high and passes an audio signal from a source to an output.

I fear that a relay hardly blink when the wave has a high frequency (do not have time to switch, when the waves are too dense), and also the relay is cumbersome and expensive.
A friend of mine advised me to use a transistor as a switch. When OFF is interdiction. When is ON, it passes the input signal.
What should I apply voltages to the transistor? And how to connect?

The audio signal to drive the order of millivolts (actually thinking of an input type guitar or keyboard) and it must be perfectly reproduced on the transistor's output.

I hope I have given all possible information. I am attaching a diagram anyway:



I state that I'm not very versed in electronics.

Thanks a lot.

Luca.

[Nigel Goodwin]

Use a CMOS switch, they are intended for this purpose.

Here#s some info from Maxim:

Selecting the right CMOS analog switch - Maxim

[Enzo]

Or a JFET.