OMB meaning in Community ?

A one-man band is a musician who plays a number of instruments simultaneously using their hands, feet, limbs, and various mechanical or electronic contraptions. One-man bands also often sing while they perform.

The simplest type of "one-man band" is a singer accompanying themselves on acoustic guitar and playing a harmonica mounted in a metal "harp rack" below the mouth. This approach is often taken by buskers and folk music singer-guitarists. More complicated setups may include wind instruments strapped around the neck, a large bass drum mounted on the musician's back with a beater which is connected to a foot pedal, cymbals strapped between the knees or triggered by a pedal mechanism, tambourines and maracas tied to the limbs, and a stringed instrument strapped over the shoulders (e.g., a banjo, ukulele or guitar).

Since the development of Musical Instrument Digital Interface (MIDI) in the 1980s, musicians have also incorporated chest-mounted MIDI drum pads, foot-mounted electronic drum triggers, and electronic pedal keyboards into their set-ups. In the 2000s and 2010s, the availability of affordable digital looping pedals has enabled singer-musicians to record a riff or chord progression and then solo or sing over it.