SN76477 "complex sound generator" is a sound chip produced by Texas Instruments (TI). The chip came to market in 1978. A compatible version is identified as ICS76477.

The SN76477 was essentially a synthesizer on a chip, and was intended to be used with external controls like potentiometers and keyboards that would control the output. Many of its advanced features like envelope control required external circuity to implement. Moreover, the internal model was based on the concept of one-shot sounds, in which a particular tone would be generated once for a specified time when triggered by an external signal, like a keypress.

The chip was used as a sound effects generator in arcade games and toys and for hobby projects. Among its better-known uses is the arcade game Space Invaders. More recently, it has been used as a hobbyist system for building simple analog synthesizers, using it with various external controllers.

In 1979, TI released the Texas Instruments SN76489, which had fewer features but was much easier to integrate into systems, and saw considerably wider use in the market.

The SN76477 was an advanced design for its era, including three voltage-controlled oscillator (VCO) tone generators (or "voices") that can be played at the same time to produce three-note polyphony. It also had a "super low frequency" oscillator (SLF) designed to be a control source that would be used to control the output of the three main voices, for instance, by turning a selected VCO output on and off at a given rate. A similar circuit added noise that can be mixed into the other voices, or gated by the SLF to produce its own percussion-like sounds. Additionally, the system included an envelope generator with controls for the attack and decay times, as well as the sustain level. The output of any of the channels was further controlled by an on/off switch, or a separate "one shot" switch that would play a given channel for a pre-specified time and then stop.

The combination of these features made it among the more advanced sound chips of its era, with only the General Instrument AY-3-8910 offering some level of parity, although it lacked the SLF and the effects it could create. However, the SN76477 lacked any internal state, and all of the control inputs had to be provided through external circuity connected to various pins, whereas most sound chips included internal processor registers that controlled internal circuitry to provided these controls. This made the SN76477 significantly more difficult to implement; for instance, using the envelope generator required connecting three pins to resistors to provide reference levels for the attack, decay and sustain levels, and a capacitor to control the timing of the attack and decay. Even selecting the pitch for one of the VCOs required external circuits.

There were two different sizes of the SN76477 available. The SN76477N was in a standard 0.6 in (15.24 mm) width dual in-line package (DIP). The SN76477NF was in a less common 0.4 inch (10.16 mm) width DIP. The SN76488 is similar to the SN76477 but with internal audio amplifier.

The following quotation summarizes its facilities: