Categories of Form, Sound, Scent, Taste, and Tangible Objects

Form, sound, scent, taste, and tactile sensation are each classified into several types. The first volume of the Yogācārabhūmi-śāstra discusses the classification of sounds, dividing them into several kinds. The sense object of taste is also divided into several types, some arising from the Tathāgatagarbha within sentient beings themselves; the sense object of touch is similarly classified, and so is the sense object of scent. Dharma objects, combined with the five sense objects, are also simultaneously classified into several types.

Sounds may arise from the interaction of the physical body and the external environment; some are purely external sounds, while others are produced through the interactions between sentient beings. The sounds generated by a sentient being themselves are produced solely by their own Tathāgatagarbha. Sounds emanating from within the body are also divided into several kinds: those produced by the control of the mind-consciousness through perception and contemplation; those arising from the processes of food absorption and digestion; those generated by pathological changes in internal organs; those produced by the manas regulating chewing and swallowing during eating and drinking; those arising from gastrointestinal peristalsis; those generated by autonomous respiration; and those produced by the functioning of internal organs, such as the sound of the heartbeat.