Wavetable synthesis is a sound synthesis technique used to create periodic waveforms. Often used in the production of musical tones or notes, it was developed by Wolfgang Palm of Palm Products GmbH (PPG) in the late 1970s  and published in 1979, and has since been used as the primary synthesis method in synthesizers built by PPG and Waldorf Music and as an auxiliary synthesis method by Ensoniq and Access. It is currently used in software-based synthesizers for PCs and tablets, including apps offered by PPG and Waldorf, among others.
Wavetable synthesis is fundamentally based on periodic reproduction of an arbitrary, single-cycle waveform. In wavetable synthesis, some method is employed to vary or modulate the selected waveform in the wavetable. The position in the wavetable selects the single cycle waveform. Digital interpolation between adjacent waveforms allows for dynamic and smooth changes of the timbre of the tone produced. Sweeping the wavetable in either direction can be controlled in a number of ways, for example, by use of an LFO, envelope, pressure or velocity.
Many wavetables used in PPG and Ensoniq synthesizers can simulate the methods used by analog synthesizers, such as Pulse Width Modulation by utilising a number of square waves of different duty cycles. In this way, when the wavetable is swept, the duty cycle of the pulse wave will appear to change over time. As the early Ensoniq wavetable synthesizers had non resonant filters (the PPG Wave synthesizers used analogue Curtis resonant filters), some wavetables contained highly resonant waveforms to overcome this limitation of the filters.
In 1992, with the introduction of the Creative Labs Sound Blaster 16 the term "wavetable"  started to be (incorrectly) applied as a marketing term to their sound card. However, these sound cards did not employ any form of wavetable synthesis , but rather PCM samples and FM synthesis. S&S (Sample and Synthesis) and Digital Wave Synthesis was the main method of sound synthesis utilised by digital synthesizers starting in the mid 80's with synthesizers such as Sequential Circuits Prophet VS, Korg DW6000/8000 (DW standing for Digital Wave), Roland D50 and Korg M1 through to current synthesizers.
The creation of new wavetables was previously a difficult process unless supported by specialized editing facilities and (near) real-time playback of edited wavetables on the synthesizer. Such editors often required the use of extra hardware devices like the PPG Waveterm or were only present in expensive models like the Waldorf WAVE. More commonly, pre-computed wavetables could be added via memory cards or sent to the synthesizer via MIDI. Today, wavetables can be created more easily by software and auditioned directly on a computer. Since all waveforms used in wavetable synthesis are periodic, the time-domain and frequency-domain representation are exact equivalents of each other and both can be used simultaneously to define waveforms and wavetables.
During playback, the sound produced can be harmonically changed by moving to another point in the wavetable, usually under the control of an envelope generator or low frequency oscillator but frequently by any number of modulators (matrix modulation). Doing this modifies the harmonic content of the output wave in real time, producing sounds that can imitate acoustic instruments or be totally abstract, which is where this method of sound creation excels. The technique is especially useful for evolving synth pads, where the sound changes slowly over time.
It is often necessary to 'audition' each position in a wavetable and to scan through it, forwards and backwards, in order to make good use of it, though selecting random wavetables, start positions, end positions and directions of scan can also produce satisfyingly musical results. It is worth noting that most wavetable synthesizers also employ other synthesis methods to further shape the output waveform, such as subtractive synthesis (filters), phase modulation, frequency modulation and AM (ring) modulation.
Table-lookup synthesis (or Wavetable-lookup synthesis) (Roads 1996) is a class of sound synthesis methods using the waveform tables by table-lookup, called "table-lookup oscillator" technique. The length of waveforms or samples may be varied by each sound synthesis method, from a single-cycle up to several minutes.
The term "waveform table" (or "wave shape table" as equivalent) is often abbreviated to "wavetable", and its derive term "wavetable oscillator" seems to be almost same as "table-lookup oscillator" mentioned above, although the word "wave" (or "waveform", "wave shape") may possibly imply a nuance of single-cycle waveform.
However, a derive term "wavetable synthesis" seems slightly confusing. In a natural usage of words, its original meaning is basically same as "table-lookup synthesis", and possibly several actions on waveform(s) may be expected, as seen on a paper about Karplus-Strong string synthesis (a simplest class of "wavetable-modification algorithm" known as digital waveguide synthesis). Then in the late-1970s, Michael McNabb and Wolfgang Palm independently develop the multiple-wavetable extension on the table-lookup synthesis[note 1] which was typically used on PPG Wave and known with wavetable sweeping, and it was later referred as "multiple wavetable synthesis" by Horner, Beauchamp & Haken 1993. Simultaneously since late-1970s, also the sample-based synthesis using relatively long samples instead of single-cycle waveforms, have become influential by the introductions of the Fairlight CMI and E-mu Emulator.
On the above four terminologies for the classes of sound synthesis methods, i.e.,
if these had been appropriately used to distinguish each other, any confusions could be avoided, but it seems failed historically. At latest in the 1990s, several influential sample-based synthesis products were marketed under the trade names similar to "wavetable synthesis" (including Gravis Ultrasound wavetable card, Creative Wave Blaster wavetable daughterboard, and Microsoft GS Wavetable SW Synth), and these confusions have further affected on the several industry standards (including MPEG-4 Structured Audio algorithmic and wavetable synthesis, and AC97 optional hw acceleration wavetable synth). As a rebound of these, at the latest since the mid-2000s, a new confusion seem to begin flourish. Merely a subclass of generic wavetable synthesis, i.e. McNabb and Palm's multiple wavetable synthesis, tends to be erroneously referred as if it was a generic class of whole wavetable synthesis family, exclusively.
As a background of these confusions, the difficulties of maintaining the consistencies between concepts and terminologies during the rapid developments of technology, may be significant. And it is a reason why this slightly classical terminology "Table-lookup synthesis" is explained on here.
The samples in the wave shape table ...", "FIGURE 1 ... 16 K × 14 BIT WAVETABLE
SOS contributor Steve Howell replies: Wavetable synthesis is actually quite easy to understand. In the early days of synthesis, (analogue) oscillators provided a limited range of waveforms, such as sine, triangle, sawtooth and square/pulse, normally selected from a rotary switch. This gave the user a surprisingly wide range of basic sounds to play with, especially when different waveforms were combined in various ways.
Wavetable Synthesis: One standard synthesis technique is the wavetable synthesis algorithm. ... The wavetable-synthesis technique is very simple but rather dull musically, since it produces purely periodic tones. ... All the algorithms described in this paper produce the variation in sound by modifying the wavetable itself.
Multiple wavetable synthesis, the subject of this paper, is based on a sum of fixed waveforms or periodic basis functions with time-varying weights.
2.2 Wavetable synthesis with SASBF: The SASBF wavetable-bank format had a somewhat complex history of development. The original specification was contributed by E-Mu Systems and was based on their "SoundFont" format . After integration of this component in the MPEG-4 reference software was complete, the MIDI Manufacturers Association (MMA) approached MPEG requesting that MPEG-4 SASBF be compatible with their "Downloaded Sounds" format . E-Mu agreed that this compatibility was desirable, and so a new format was negotiated and designed collaboratively by all parties.
Figure 2. AC '97 System Diagram: AC '97 Digital Controller / Optional hw acceleration / SRC*, mix*, 3D positional*, wavetable synth*