I can't express it in music terms, but it's all a matter of timing. A dash is three dits long. The space between dits is the length of one dit, the same 'dit' between dashes. And the space between characters is one dash. between words is about two dashes (all this is approximate!). There are variations in that spacing which accounts for someone's 'fist', you know, so my fist isn't going to sound like your fist, or anyone elses. It also depends on your familiarity with CW. After a while your mind makes it sort of 'automatic' to a point. Unless it's mechanically or electrically controled, there is no such thing as 'perfect' CW. Sure, you want to try for it, but don't hold your breath.
A comma is '--..--', and a period is '.-.-.-' , at least in international Morse code. Oh, and then you can get into some 'short cuts' with numbers! That's a matter of operational procedure/habit/weird stuff. People who do a lot of numerical stuff use some 'abbreviations', a shorter way of sending numbers. It isn't very typical using keyers, but 'speed keys'/bugs are capable of it. Instead of the normal '.----' for one, it's sent as a '.___' (that '_' is just a very long dash). for a five, '.....', just a single dit is sent. Any multiple part of a character, both dits and dashes are shortened to either one dit or a long dash. Make any sense to you? Probably not until you've listened to CW for a while. Think of it as a 'lazy' way of doing it, not as much work with a straight key? It takes a lot of experience to get to that point so don't even think about it till you get there! Always something to make it more complicated, right?

- 'Doc
Your ears/mind can compensate for more than you'd/I would ever believe...