Analog Music Computer for Eurorack. Buchla's legendary 257 and 281 analog synthesizers are considered classics of their genre, implemented in a wide range of musical applications. The Behringer ABACUS is modeled after these original instruments, featuring an array of linear, logarithmic and exponential triggered or continuous functions. The ABACUS can generate musical envelopes or LFO signals up to 25 minutes in length and as fast as 1 kHz. Designed for use with other modules, it also allows you to change the modulation depth, modulate backwards and create even more musical events by manipulating tempo. Up to 4 control voltages can be combined to generate even more complex modulations.