In audio recording, latency is the delay introduced by the analog-to-digital conversion process, computer processing, and digital-to-analog conversion on the way back. A total roundtrip latency of more than 10–15 milliseconds becomes perceptible as an echo and makes singing or playing in time very difficult.
Audio interfaces tackle latency in two ways. Direct monitoring routes the microphone signal directly to the headphone output with zero measurable delay — bypassing the computer entirely. This is the simplest solution for tracking vocals. Most modern interfaces including the Focusrite Scarlett series have a direct monitoring switch.
Software-based low-latency recording requires a small buffer size in your DAW settings. A smaller buffer size means less latency but requires more CPU processing power. At 64 or 128 samples buffer size, most modern computers achieve total roundtrip latency under 10 ms.
USB interfaces typically achieve lower latency on Mac than on Windows, because macOS includes Core Audio — a low-latency audio driver. On Windows, ASIO drivers (provided by the interface manufacturer) are required for professional low-latency performance.