1. An apparatus comprising one or more processors and one or more memories, the one or more processors configured to: compare an input audio signal having a component to a first delayed version of the input audio signal and a second delayed version of the input audio signal to produce a multi-dimensional model; calculate a strength of each extremum from a plurality of extrema of the multi-dimensional model based on a value of each adjacent opposite extremum of the multi-dimensional model by calculating an interpolated value of the multi-dimensional model at each extremum from the plurality of extrema based on the value of each adjacent opposite extremum, the strength for each extremum from the plurality of extrema being a difference between the interpolated value for the multi-dimensional model for that extremum and a value for the multi-dimensional model for that extremum; identify a first extremum from the plurality of extrema having the strength greater than the strength of the remaining extrema, the first extremum being associated with a pitch of the component of the input audio signal; and extract the pitch of the component from the input audio signal based on the strength of the first extremum.