As you upgrade in quality from one instrument to another, the amount of overtones produced by the instrument increases. Overtones are what makes an instrument universally appealing. They make the sound inherently interesting and allow you to insert emotion into pieces. The more overtones an instrument produces the more you can express yourself and evoke different tonal colors.
Overtones are produced by the individual pieces of wood freely vibrating at different frequencies. When we hear those frequencies along with the fundamental pitch that is being played the sound is more interesting to the listener, regardless of musical background. Though they will generally fall below the level of conscious awareness to the untrained ear, overtones are none-the-less able to be perceived by the general population.
Overtones are what allow an individual soloist’s violin to be heard over a symphony orchestra composed of over 100 musicians. The soloist’s instrument produces the most complex sound on stage which allows us to distinguish it over all the other instruments on stage.