“…A number of factors extraneous to fundamental frequency have influence over the perception of relative pitch. For example, the perception of relative pitch can be influenced by pitch register (Russo & Thompson, 2005a), loudness (McDermott, Lehr, & Oxenham, 2008;Thompson, Peter, Olsen, & Stevens, 2012), facial movement (Abel, Li, Russo, Schlaug, & Loui, 2016;Thompson, Graham, & Russo, 2005;Thompson, Russo, & Livingstone, 2010) and brightness (Allen & Oxenham, 2014;McDermott et al, 2008;Russo & Thompson, 2005b). With regard to the latter, note-to-note changes in brightness that are congruent with changes in pitch have been found to lead to an expansion of perceived interval size (i.e., pitch distance), whereas incongruent changes lead to a contraction.…”