Tempo as in rhythm.
Is it necessary? Think of all of the techniques in kata that are performed slowly and then a following technique fast. Would you ever perform that sequence with that same rhythm even when doing the bunkai on a practice opponent?

In Goju kata at least, most of the slow movements are defensive, while most of the fast movements are in the offensive. why is that? I can see the merit of performing the entire kata slow for perfecting technique and balence, but I fail to see why the tempo would not be: fast sequence...pause...fast sequence...pause...etc. throughout the kata.

Could it be that esthetics in tempo and/or form were built into the kata even early on, which was further modified thru generations? or is there merit that I am not seeing? (or forgetting).

Thank-you in advance for your thoughts.
-Ed

Tempo in kata is related to timing. In Matsubayashi there is no defense, only attack. All movements are designed to actually attack, or set up an attack that follows immidiately. Striking in combination with the same rhythm makes your attacks easy to avoid. When striking in combination the tempo must change. In general I increase tempo to exploit and opening and I decrease tempo to create an opening.

There are a few reasons. One is the asthetic value of broken rhythm & another is the practical value of broken rhythm. Other reasons are breathing (inhale fast, exhale slow), strengthening (extended times in difficult stances), the eb & flow of hard & soft to create power from relaxation (Go & Ju), meditative & memory aid (sequences of like technique).

I typed a long response, but accidentaly hit back and lost it

Medulant and hedkikr made great points on the training value in broken tempo: breath regulation, timing etc.

I will say this though:

Modern kata performances have excessive, dramatic pauses mid-technique. This is unnecessary. These static, deadlocked positions are a result of the problem in transmission of karate to Japan and to the USA. This was furthered as time went on for sake of aesthetics. Dynamic, continuous body motion should never be sacrificed for the sake of visually pleasing broken rythm.