time interval, separation, musical interval, subinterval, period, duration, elapse, interburst, sequence, interpulse, more...

continuous, constant, unbroken, ceaseless, uninterrupted

semitone, whole tone, minor third, major third, perfect fourth, perfect fifth, minor sixth, major sixth, minor seventh, more...

short, longest, brief, same, second, year, certain, free, considerable, average, minute

time between events,   portion of time,   time duration,   time gap,   empty space between,   time between,   the space between,   such spacing,   intervening time,   break between