The Roland SYSTEM-500 540 Dual Envelope Generator and LFO is a multi-purpose modulation source module designed in eurorack format to fit in Roland's SYSTEM-500.

The unit features two independent ADSR (attack, decay, sustain, release) envelope sections that produce variable voltages for controlling other Eurorack format synthesizer modules such as oscillators, filters, and VCAs. Each section can be triggered externally, internally, or manually with dedicated jacks for each envelope, as well as an inverted output.

Additionally, the 540 includes a voltage controlled LFO with 5 waveform outputs. Front panel controls adjust both frequency and delay time of the LFO start. Delay and reset can be triggered from either envelope 1 or 2.