The gesture behind `illuy ("elevated"), as reconstructed by me, is the only gesture that (like the written sign that transcribes it) has a dual meaning that depends on its melodic context. (In the photo below, the gesture is turned 90 degrees forward from where it should be if the positioning is to be consistent -- though as I mention in the main text, what is truly important is the relative geometry of the hand-gestures, not the relative positions of the hands.)

When
`illuy (as it does frequently) follows silluq (when the latter acts as "ga`ya"), or when it begins a verse, or when it follows merkha, it always denotes a rise of a fifth (perfect or diminished) above the sustained degree. When it follows tifha, atnah, or munah (according to Haïk-Vantoura's table for the psalmodic system), it may mean either a rise to a fifth above the sustained degree or a descent to a fourth below the sustained degree. When it follows mehuppakh (as it does frequently), it always denotes a descent to a fourth below the sustained tone.

Why this duality? As Haïk-Vantoura notes in her book (p. 343), if `illuy always represented a rise of a fifth above the sustained degree, it would often take the melodic line to unhabitual heights. (In effect, the overall melodic line would transcend its normal ambitus, and the specific ta`am would give an extreme and inappropriate pitch inflection to the word it marks.) The solution is actually very simple: when it follows a high sustained degree, `illuy then signifies a functionally equivalent inversion of its usual tonal value. This keeps the melodic line within its usual ambitus of eleven degrees, and also accents the specific word appropriately in every case.

Updated December 27, 2011