noun
1. : an instrument that obtains a sound spectrum by analyzing a complex sound into its component elements
2. : an electronic instrument that produces a time-frequency-intensity analysis of sound recorded on a magnetic tape loop by repeatedly playing the sound into a variable filter and recording the output by means of a stylus on electrically sensitive paper and by synchronizing the movement of the tape loop and the paper so that successive lines drawn by the stylus along the horizontal axis of the paper correspond to the shifting frequency range of the filter