Shadow

When a simple (i.e. low integer-limit) ratio and a sufficiently more complex ratio are sufficiently close in cents, the complex one is generally perceived as a tempered version of the simpler one. The simpler one is said to overshadow the more complex one. The simpler ratio's shadow size refers to how many cents it takes to be sufficiently close, and the simpler ratio's shadow is that range of cents both above and below that ratio. The simpler the ratio, the larger its shadow is. But shadow size is somewhat subjective, and tends to decrease with microtonal ear training.

For example, 32/21 at 729¢ is often perceived as 3/2 widened by 27¢. Whereas 14/9 at 765¢ is generally perceived as a distinctly different interval than 3/2. Thus 3/2's shadow size, at least to the untrained ear, is at least 27¢ (64/63) but less than 63¢ (28/27).

Shadow size is dependent on voicing: 21/16 is less often perceived as overshadowed by 4/3, because the two integer limits are closer. And 21/8 is even less often overshadowed by 8/3. Likewise, while 6/5 overshadows 19/16, 19/4 overshadows 24/5 (cents distance of 96/95 = 18¢ in both cases).

While a ratio in isolation has a specific (subjective) shadow size, context has an influence. For example in 12:14:16:19, 19/16 is generally not perceived as a tempered 6/5.