Marcus began his professional industry career as a design engineer at the synthesizer company Oberheim Electronics. From 1980 through 1985 he was a key architect and designer of such instruments as the OB-Xa, OB-8, Xpander, and Matrix-12, as well as the DSX sequencer and DMX drum machine. In 1996, Marcus cofounded Line 6, a leading developer of guitar amps and effects simulation technology. In 2014 Line 6 was acquired by Yamaha where he helped to spearhead the company's guitar division. Today Marcus runs a consulting firm called WRiiG, providing technology and business consulting to music technology companies.