Methods and apparatus to generate signatures representative of media are disclosed. An example method includes transforming a block of samples from a time-domain representation to a frequency-domain representation comprising multiple frequency bands, determining a signature function by fitting a curve to at least a subset of the frequency bands, and calculating signature values for the block. Calculating the tuple includes calculating a first angle between a reference line and a first line that is tangent to the signature function at a first index, calculating a second angle between the reference line and a second line that is tangent to the signature function at a second index, calculating a third angle between the reference line and a third line that is tangent to the signature function at a third index, and creating the signature values based on the first angle, the second angle, and the third angle.