Described is a method of generating a flow having a composition gradient. A plurality of pump strokes is generated for each pump in a plurality of pumps. Each pump stroke has an initiation time and provides a volume contribution of a liquid to be mixed in the flow according to the composition gradient for the flow. The pump strokes of the pumps are controlled so that a sum of the volume contributions of the liquids that occurs between consecutive initiations of one of the pumps is maintained at a constant value throughout the duration of the flow. For each pump, the flow rates and the times between stroke initiations can change as long as the sum of all volumes contributed between the consecutive initiations of one of the pumps is held constant. Advantageously, the method achieves a constant compositional noise characteristic throughout the duration of the flow.