Hm, lots of interpretations here.
If you're looking for a genre where the songs are primarily computer-synthesized music, I'd call that "electronic music", but this usually comes with some implicit awareness that you're referring to a particular style of music. e.g., most people think of electronic music along the lines of techno, EDM, chiptune, etc., whereas they might not classify a transcription of "classical music" played in MIDI as electronic music.
If synthesizers are the dominant instrument, I'd call it a "synth band" or a "synthpop band".
I noticed your emphasis on "tablet computers". If you mean tablet computers are necessary to the performance or recording, maybe you mean "Controllerism"? They use tablet computers (along with hacked-together electronic instruments of their own design) to compose and perform music.