Which musical instrument, originating from Aztec culture, is made of clay and features abstract decorations?

The ocarina is the correct choice as the musical instrument originating from Aztec culture, made of clay and featuring abstract decorations. The ocarina is a small wind instrument, traditionally made from ceramic or clay, that resembles a rounded vessel with finger holes for pitch control. Its design often incorporates intricate, abstract ornamentation, reflecting the artistic styles of its creators.

The tlapitzalli, while a traditional Aztec flute made from wood or reed, does not match the description of being made of clay or featuring abstract decorations. The flute, in general, encompasses various types of instruments but is not specifically associated with the clay construction or the artistic embellishments typical of the ocarina's design. The harp, though a beautiful and complex instrument, is not known to be linked to Aztec culture and does not typically feature clay construction or abstract decorations. Therefore, the ocarina stands out as the best answer to the question asked.