Abstract: A method of performing spectral analysis of signals recorded by a magnetic recording or storage system is provided using a modified channel chip of the system. The modified channel chip enables measurement of harmonic components of the recorded signal. The recorded signal is a periodic analog signal having a period N. The method is performed by reading the recorded periodic analog signal and converting the signal into a discrete time periodic signal. The discrete time periodic signal is digitally sampled at predetermined intervals, and the digital samples are selectively accumulated in a register or registers of the channel chip. Incoming digital samples are accumulated by selectively being added to contents of the registers, or alternately being added and substracted to contents of a single register. The accumulated results represent summations used to determine harmonic coefficients of the recorded signal.