Many commercial software applications for timbre creation and manipulation feature an engineering-focused, parametric layout. This paper argues the case for a perceptually motivated approach to interface design in such tools. ‘Perceptually motivated’ in this context refers to the use of common semantic timbre descriptors to influence the digital representation of timbre. A review is given of existing research into semantic descriptors of timbre, as well as corresponding acoustic features of timbre. Discussion is also given on existing interface design techniques. The perceptually motivated approach to interface design is demonstrated using an example system, which makes use of perceptually relevant mappings from acoustic timbre features to semantic timbre descriptors and visualises sounds as physical objects.