tone variator
...that the invention of the tone variator in 1897 marked the advance beyond classical psychophysics, as it allowed the study of the perception of continuous changes in stimuli?
...that the invention of the <b id="mwB00"><a href="./Tone_variator" id="mwB04" rel="mw:WikiLink" title="Tone variator">tone variator</a></b> <i id="mwB08">(pictured)</i> in 1897 marked the advance beyond classical <a href="./Psychophysics" id="mwB1A" rel="mw:WikiLink" title="Psychophysics">psychophysics</a>, as it allowed the study of the perception of continuous changes in <a class="mw-redirect mw-disambig" href="./Stimuli" id="mwB1E" rel="mw:WikiLink" title="Stimuli">stimuli</a>?