Wavetable synthesis   

Given that pitch is a common characteristic in musical sound an efficient way to generate a sound is to create a digital oscillator which simply repeats a waveform at some amplitude and frequency and for some duration. 
This method gains its efficiency by virtue of its use of a lookup table which avoids complex calculations for each sample.  Using this method, when a new sample is needed for output, a table containing a set of numerical values representing one period of a waveform is searched to find the closest value corresponding to the phase needed.  Interpolation between adjacent data points can achieve greater precision. 
While this technique offers computational efficiency it suffers from a lack of timbral development.  Use of an amplitude envelope, filter, and low frequency modulation, techniques borrowed from subtractive synthesis, can help add variation to the timbre. 
See Also:
additive synthesis   FM synthesis   granular synthesis   subtractive synthesis