What is the relation between windowing and hopping in audio DSP
What many people do not seen to realize is that using a finite length transform (such as one iteration of an STFT FFT) on a longer signal already alters the longer signal by windowing (e.g. ignoring the portions of the signal that do not fit in the current finite length FFT).  Not using a tapered window means that one is using a rectangular window.  Using a rectangular window may alter the signal spectrum even more than using a tapered window (from, say the infinite length FT of an infinitely long stationary signal, especially if the signal is not perfectly integer periodic in the STFT FFT aperture width).

The FFT spectrum is altered the least near the center of the window (where a tapered window has a gain of unity or a maximum gain, and non-tapered signal is farthest from both potential edge transients).  Therefore the closer together the window centers of individual STFT FFTs (the shorter the hops), the less the alteration or distortion of the total STFT spectrum.  

Lots of overlap also provides greater time localization or locality (e.g. the STFT won't miss or slice up a short event that is right between two windows). 
 However the greater the overlap, the greater the computation required.  So a compromise overlap of 50% or 75% window overlap is common.