How does one get the length of an array?

Programming and Development New Plug-Ins
1

I have a few tracks that I want to ensconced into an array…
But in order to have a program automatically apply itself to such an array, one would need to know the length of said array…
Also if an array has 7 sounds in can I get the last one by (aref array-name 6) ?
IOW does the array construct work somewhat like a list?

2 
(setf my-array (vector 10 20 30 40 50))  ;create a named array with 5 elements

(print (length my-array))  ; prints 5

(dotimes (i (length my-array))
  (print (aref my-array i)))  ;prints 10 to 50