According to the Wikipedia entry Lucien Goethals 'was a stubborn proponent of "high" culture', which may seems surprising considering he was in at the start (1962) of IPEM, Belgium's studio for experimental music (see here). Then again, as you know, many pioneers of electronic music came from modern classical backgrounds. Whether the music here would be considered 'high' or 'low' is a matter for each listener, although I'm sure many a classical purest in the 60s would have been scratching his beard in puzzlement at the sound of all this alien electronics.
Difonium succeeds in marrying the old world (clarinet, cello, piano) with the new (tape noise). The clarinet is most prominent with minimal hits from the piano punctuation proceedings, but it's the way Goethals matches clarinet with 'noise' that makes it so brilliant, almost in a call and response fashion, or conversation anyway. Cellotape is also electroacoustic, a more complex interaction between cello (plucked and bowed), piano and electronics. Understated but all the more gripping for being so, when certain sounds leap out the impact is greater than if they were continually making their presence felt (that crashing piano!). Studie VII B is purely electronic, the depth of sound provided by deeper tones (heavily echoed) whilst other sounds dance across the surface. These tracks prove that Goethals was as adept at fusing traditional orchestral elements with 'modern' as he was exploring the new. Essential.