Frank Martin was a Swiss composer. No, I hadn’t heard of him either.
Le vin herbé (The Potion), composed 1938–1940, is Martin’s version of the Tristan and Iseult story, or at least the “love potion” part. It’s rarely staged but was performed by the Welsh National Opera in April 2017.
Tristan and Isolde drink a goblet of wine together, not knowing that it is actually a love potion that was intended for the elderly King Marke, to whom Isolde is married. The king hears of their relationship and condemns Tristan to death… I won’t spoil the ending.
Two hours of this is a bit easier to digest than 5+ hours of Wagner…