I would like to make a guitar signal level, audio switching circuit. I was thinking a 4066 or 4053, but I don't know how these might degrade the signal. Are they ok, or are there some specifically designed ICs that are better. thanks
I've worked with the 4066. It's easy to use. Suitable for AC signals in either direction. Many schematics use it in audio projects, which implies it has low distortion. The min/max resistance is suitable for low amplitude waveforms.
Klaus is right of course but I have used 405x and 4351 (the latched version of 4051) in broadcast applications very successfully. In fact they have been used for thousands of hours in TV broadcast without any complaint and they have switched video as well as audio. As long as the DC voltages at each side of the switch are close to each other there should be no problem and noise injection through the control port is too low to notice.
The 'on resistance' curves for the CMOS switches show they are reasonably linear over small signal excursions.