Try this. Rather than using "tah kah tah kah" try using "doo goo doo goo". For regular tonguing I prefer the "d" syllable as opposed to the "t" syllable, so this method of double tonguing I think doesn't change how I already tongue normally. Plus the "goo" motion I think is less harsh and striking at the "kah" syllable. Start slow! Try practicing articulations with just the "goo" syllable (goo goo goo goo) to get the motion down in your throat. Whatever your speed is with just goo's, double that, and that's your potential double tongue speed. POTENTIAL, you still have to slowly work it up. Then start to incorporate using the tongue (doo) and the throat (goo). I've been working on this for a while, and am still not entirely comfortable with it. It's been a few months, but it's getting there. Bravo for working on the Sequenza! I think it's an amazing piece in our repertoire. Listen to clarinet players do it (Paul Meyer, Alain Damiens, etc...). Also, not all of them double tongue that section you're talking about. My favorite recording of this is in a 3 disc set called Sequenza, which contains all of the Berio Sequenzas played by members of the Ensemble Intercontemporain. Christian Wirth (soprano player for Quatuor Habanera) plays the saxophone sequenzas. ABSOLUTELY AMAZING! Good luck on the double tonguing and the Berio!

Check out Wiedoeft's Secret of Staccato book. Also, look into tuk-kuh-tuk-kuh. Or you may just practice your single tonguing until you reach the tempo you desire. For that piece, I believe it's possible to use a single tongue.

Double-tonguing, specific to the saxophone family, is a technique that has been slow to gain acceptance in the U.S. Many teachers/players in the States still consider it either a crutch or a technique "only for show." Due to this, there are only a few sources of sound pedagogical information on the technique in the states. This is not the case in Europe and especially France, where players have been teaching and using this technique in many genres of saxophone playing for at least the past twenty years. I've been working on the technique for around five years, and can share the following insights with you. My double-tonguing speed approaches 16th notes at quarter=200 for short passages, and quarter=170-180 for sustained durations. First, the level of resistance provided by your setup can help or hinder your progress -- especially in the early stages. Resistance plays a large part in the process, since the back of the tongue and accompanying glottal motion are responsible for the second syllable (kah, kuh, gu). Say the syllable "ku"or "gu" and with your finger, feel the contact point between the back of the tongue and palette. This is where you produce the second articulated syllable. First practice only the "gu" syllable, with the metronome, once per beat on a scale of your choice. I recommend "gu" in the beginning because it leads to a legato approach. Double-tonguing does not require staccato sylables, and too sharp of a second syllable "ku, kah, etc" can actually slow your maximum speed. Try to achieve a clear, precise attack. If this is no problem, try 2 "gu's" per beat, sustaining the air constantly behind your attacks. Imagine that you are skipping a rock, or skimming your syllables across the surface of your air -- you want minimum disruption/break between the two syllables. Speed is not of the essence at this point. Work towards a goal of (2) "gu" syllables at quarter note=120 for the duration of a full breath. This is the first step, and must soon combined with reflexive speed drills which combine the two syllables into the full double-tongue technique. Good luck.