For time-delayed audio, we need to create what's called a "circular buffer" or a "ring buffer", an array of samples to which we record continuously in a loop, and which we can then use always to access the most recently recorded sound from the past.
This example shows how to create a buffer~ that always contains the last ten seconds of audio coming out of and adc~.
Preloading sound into random-access memory (RAM)—as opposed to reading it off of a hard disk—allows you more easily to access any point in the sound file instantaneously, read backwards as well as forwards, access different points in the sound simultaneously, etc.