Okay, I'll have to hum along on this one.

Mo, I've had similar issues with my very own attempts at kazooing and I've played around with the dern things for a long time. Many have already pointed out that there are two causes as to why kazoos will or won't work well. Each of these stem from the only two moving parts involved in this activity 1. the membrain that vibrates on the Kazoo itself and 2. the person vibrating it.

In my own experiences at trying to get the best sound from my attempts at playing kazoo I thought that perhaps exploring the differences in the way they've been made over the years might prove that some kazoos are better than others at the task. I've collected as many older examples as I could find, hoping to locate an Excaliber among kazoos, but I'm not certain that I've really had much luck in doing so. While I've found that the differences in design among these little hummers to be at least partly responsible for their ability to do the job, I'd have to say that the greatest share of what can be accomplished with them is due playing to technique.

That said, I like you Mo have endeavored to ask questions. I've approached those who I heard producing the best kazoo technique. This has been of limited value because it seems that some folks merely have what it takes naturally. While others, like myself, must struggle in their attempts at everything musical to attain a desired level of competency. Now, even with years of half hearted practice at the kazoo, I am still only a mediocre player. This outcome has caused me to leave my kazoo perched atop my stereo speaker at home more often than not.

In my more determined efforts at trying to capture the particular technique that I was hoping for I recall that I had the greatest difficulties with the only moving part on the kazoo, the vibrating membrain. This is certainly the main, no, only key component of most of the kazoos made today. If it is not functioning correctly you get little or no response for all your efforts.

My kazoo of choice was a metal bodied Kazoozaphone. This was a standard metal bodied kazoo that had been produced for many years by the Kazoo Co. mentioned in a previous post, but also included a sousaphone stlyed bell above the membrain's chamber. These kazoos featured a twist off top to the membrain's chamber so that the membrain could be adjusted or changed if damaged from overexuberant kazooing. I know that this sounds unbelievable but in fact the membrains used to be made of a very sensitive material that could be damaged. When this happened they would need to be replaced. At one time the avid player could purchase replacement membrains from the factory but I don't think that they're available anymore.

The one other factor that I had the most difficulty with is making certain that I had the top to the chamber screwed down to the proper tension. Too much tension, or too little, on the membrain seemed to alter the way it could respond. The design of the threads that help this part of the kazoo to stay in place are rather poor and so it would often work its way loose. I used to mount my kazoo in my harmonica rack on my washboard or on the rack that I used around my neck and the vibrations associated with changing harmonicas or my foot stomping or scubbing would all contribute to shaking loose the membrain chamber's lid.

If you have an adjustable top to your membrain's chamber on your kazoo, keep your lid tight. Find an adequate source for replacement membrains as others have suggested and practice, practice, practice.