Their last participation was in 1981 which also gave the group its best result. Io senza te was a passionate Italian ballad, which in Italy's absence and with a perfect place in the running order (19th song sung among 20 entries) struck the right chord among the audience loving the mediterranean ballad. After a very narrow voting Switzerland ended fourth just 16 points short of winning the contest altogether.
That was maybe a good thing. The song, composed by Peter Reber from the group, included a instrumental passage played, apparently, with a pan flute. According to some sources the sound of the flute came from the backing tape. As the acoustic instruments were not allowed (in 1981 that is) to be pre-recorded, the song would probably have been subject to protests if the it had won.
Year 1981 marked the end to the 10 year run of the group. After that the three singers have performed together only occasionally.
The Swiss entry remains one of the most enduring songs from the 1981 contest often dismissed for being full of second rate disco ditties. To me, Io senza te would have been a perfect winner.
My points 4/5.