Split Tones (son fendu) and Xenakis


One of my favorite pieces for trombone solo is Keren by Iannis Xenakis.

In my opinion it is one of the best pieces ever written for trombone solo, next to Berio’s Sequenza, and I often wonder why it’s not performed more. I know it’s difficult, especially the 3rd page, but I think it’s definitely worth working on by ambitious students and professionals alike. In fact, if my memory is correct, it was one of 3 contemporary music pieces to be chosen from in the 2nd round at the ARD competition in Munich 2007.

What always surprises me though is, when talking to other classical trombonists, who are not experienced in new music, that they really don’t know what to do with the double note passages, the ones with the notes in parenthesis below the main note. Most seem to think it’s just normal multiphonics, singing and playing. This is most definitely not the case. Unfortunately, there is no explanation in the part, but there is an explanation in another work of Xenakis’ from the same year 1986. It’s an ensemble work called Jalons, written for Ensemble Intercontemporain and trombonist Benny Sluchin for whom Keren was also written. Much of the material in the two pieces is similar and in Jalons Xenakis uses split tones extensively in the woodwinds and trombone.

At the first split tone passage for the trombone he writes;

son fendu ou multiphonique labiale (produite par les lévres uniquement et n’incluant pas la voix). Elle est basée sur la note du haut ayant comme patiel voisin la note en parenthése du bas.

My French isn’t all that great but what I can decipher is that he wants both notes to be played with the lips only with no voice at all.

So how is this to be done?

In my experience, the best way to execute a split tone is to aim for the upper note, push the lower jaw a bit forwards and purse the lips a little more than normal. Out of the upper note a second, lower note should come out simultaneously. This note should be the next lower harmonic, so depending upon where you play it it can be a different interval. f-Bb in 1st position, f-C in F1 (or 6th position) or f-db in F5 (V) position with the valve. Xenakis uses many of these options in both pieces.

Some players can do this right away, but others, including myself, need(ed) months of practice to get them to the point of being reliable. The problem with Keren is that most of the split tones come on the last page, after the extremely taxing 3rd page. You’re tired and out of breath and if the split tones don’t work you sound like a total amateur, at best. When they do work though they are incredibly effective, very rich and complex in overtones. Much more so than a played/sung multiphonic.

I have found a substitute for the split tones which works quite well in the lower register where they are very difficult to play loudly. If you play the second harmonic low f, for instance, you can adjust the speed of your flutter tongue so it lines up and gives you the upper interval of the split tone, which when done correctly can sound very similar to a split tone and can be played very loudly. One composer, with whom I have worked with recently, remarked that it isn’t really possible to alter the speed of the flutter-tongue and that this effect must be more about altering the tongue or oral cavity similar to overtone singing.

Following are four video examples (at the end of the site):

1st video: normal playing

2nd video: (voice) multiphonics

3rd video: split tones

4th video: split tones mixed with flutter tonguing


Notice the stable frequency waves with the normal tones and that the singing does not seem to affect the lip vibration waves. The split tones have a very complex frequency wave and the flutter multiphonic has a very similar, but not quite as complex frequency wave. Notice also how loud the last three flutters are compared to the lower split tones.

I did these videos with Universitätsprofessor Dr. med. Wolfgang Angerstein as a part of his Studie über Lippenschwingungen im Funktionsbereich für Phoniatrie & Pädaudiologie am Univ.-Klinikum Düsseldorf (research project on lip vibrations, performed at the phoniatric department of the university of Düsseldorf medical school).


For those of you who can’t get enough, here is a video of the complete Keren with camera in the mouthpiece (5th video).

normal tones

voice multiphonics

split tones (lip multiphonics)

split tones and flutter tongue

Xenakis - Keren