Two approaches to the study of musical sound timbre are described and documented by psychoacoustic experiment examples. The classical bottom-up approach is demonstrated on the study of contexts of violin sounds and pipe organ sounds. Verbal attributes collected during listening tests were used for the interpretation and comparison of resulted perceptual spaces of sounds. The proposed top-down approach is based on the collection of musical experts experiences and opinions going from very common to more specific ones. Here the common perceptual space (perceptual space of verbal attributes) was constructed from nonlistening test of dissimilarity of verbal attributes describing timbre (verbal or soundfree context of stimuli). The verbal interpretation of perceptual spaces of sound contexts and perceptual space of verbal attributes are compared and the hypothesis of the four basic dimensions of timbre is formulated: 1. gloomy — clear, 2. harsh — delicate, 3. full — narrow, 4. noisy — ?.