Saturation refers to the maximum amount of magnetism a magnetic tape can hold. Attempting to add more magnetism to the tape’s oxide particles will result in distortion. Normal record levels do not generally approach saturation as distortion will be introduced before saturation is reached, especially in the low frequencies. High frequencies normally do not saturate as they have a tendency to self-erase during recording.
Engineers using analog tape often make use of tape saturation as an effect. By carefully controlling record levels, compression, warmth, and fatness can be added to a signal – all part of the much-heralded analog “mystique”.