Could be the overall combined effect of slowness, may be due to the rate data is
written & read from the hard disk drive; as the file may be saved before you hear it.
The computer configuration of memory installed (RAM total) and the data rate or
speed the storage drive (hard disk or solid state drive) plus unused capacities of
each of these, in addition to the hardware settings or limitations, can add to this.
Without knowing what else the computer is trying to do at the same time, and how
the machine is configured, the answer would be more difficult to determine. Some
computers are adequate combinations of hardware and software. And any upgrade
to one should involve a study of the effect on the other. Newer OS X will usually ask
for more RAM and more storage capacity. Faster is better, since swap files or virtual
memory, temporary caches and the like, require these extra resources for the OS X
to draw upon, automatically. The memory management is rather good in later OS X
but generally these systems use more of it, and are larger than some older ones.
So there isn't a simple answer, other than consider the lag is due to everything that
isn't faster than the speed of sound. Though electricity can be nearly light-speed,
that isn't to be expected when there are slower more mechanical processes at work.
Perhaps someone with more information about your computer build model and
resources, plus OS X version details could venture an educated guess...
That leaves me out! LOL 🙂