Grendel is a line of analog electronic music instruments from Rare Waves LLC, a Texas-based maker founded by designer Eric Archer. The brand launched in 2008 with the original Grendel Drone Commander, an analog drone synthesizer housed in a repurposed US Army ammunition can that developed a cult following among experimental musicians and producers during its 2008–2014 production run. Over 800 of the original ammo-can units were built before the project evolved into the formal Rare Waves company.

The Grendel catalog focuses on original discrete-transistor analog circuits rather than vintage reissues. Core products include the Drone Commander Classic Pedal, a stompbox-format analog drone synthesizer with true analog oscillators and a sweeping filter LFO; the Drone Commander 2 (DC-2) and its Eurorack version (DC-2e), a dual-VCO / dual-VCF analog synth voice; the Grendel Grenadier (RA-9 and RA-99), a semi-modular CV/Gate synthesizer with analog sequencer and filterbank; and the Grendel Formant Filter, a Eurorack voltage-controlled vowel filter built from four bandpass filters.

The brand is known in the Eurorack and experimental synth communities for drone, ambient, and noise-oriented instruments with a hand-built aesthetic — later units often ship in custom woodworked enclosures. Products are assembled in the USA and sold direct through rarewaves.net as well as boutique synth retailers such as Perfect Circuit, Signal Sounds, and Schneidersladen.

Grendel has 7 products cataloged on Equipboard, including Modular Synthesizers and Synthesizers. Their gear is featured by 3 artists, with the strongest followings in Electronic, Classical, and Pop. Notable users include Max Richter, Firechild, and Paul Birken.