[Inter]

For instance, if you have a mic connected to your PC or laptop via USB, and you record a signal into that mic, the signal will at it's point of origin be analogue (your voice or whatever you record), but as soon as it's been recorded by the mic, the mic will convert the signal to digital (0's and 1's) to represent that signal digitally. The reason it does this is it's the only way the USB interface the mic is connected to can understand what it's getting. It's called ADC (analogue-to-digital conversion).

Now in studios, the ADC usually does not occur in a USB mic, but at a later stage, usually in the mixing board the studio is using. For your example about Jack White, and others, who record to magnetic tape. This means the signal will travel from it's point of origin, voice or instrument, to the mic, from the mic to the board and from the board to magnetic tape, without ever being converted to a digital signal. It will be altered, as anything a signal travels through will alter it in some way, however miniscule, but it will never have been into the digital domain.