The M1 features a 61-note velocity- and aftertouch-sensitive keyboard, 16-note polyphony with 1-oscillator Programs (or 8-note polyphony with 2-oscillator Programs), a joystick for pitch-bend and modulation control, an eight-track MIDI sequencer, separate LFOs for vibrato and filter modulation, and ADSR envelopes. Data can be stored on RAM and PCM cards.
The M1 has a ROM with four megabytes of 16-bit PCM tones, including, according to Sound on Sound, "exotic instruments that previously hadn't been heard in the mainstream". The sounds include sampled attack transients, loops, sustained waveforms without attack transients, and percussive samples. The timbres include piano, strings, acoustic guitar, woodwinds, sitar, kalimba, wind chimes, and drums.
The M1 also features effects including reverb, delay, chorus, tremolo, EQ, distortion, and Leslie simulation, an innovative inclusion at the time. According to Sound on Sound, none of the M1's features were unique at the time of release, but were implemented and combined in a new way.