Money was being raised for Coniston and Lochaber mountain rescue teams which ran a 38-day search for the couple.
Rachel Slater, 24, and Tim Newton, 27, were caught in an avalanche on Ben Nevis on Valentine's day last year.
Pianist Robert Richmond hoped people at the Windermere concert took "a minute to remember Rachel and Tim".
The grand piano arrived by ferry and was carried on a special frame to Claife Heights, an elevated area above the lake.
Jack Metcalfe, a friend of Miss Slater, said she was "an incredible person" who was the "very definition of adventure".
Bringing a piano to the lake was "a reflection of her personality", he said.
The bodies of Mr Newton and Miss Slater, who lived in Bradford, were found on the north face of Ben Nevis on 23 March last year.
The experienced climbers had been missing since 15 February.
Michael Richmond, whose father organised the concert, said the couple had "strong feelings" about the mountain rescue operation.
"Following their deaths it just really emphasised how badly in need of support mountain rescue are for the phenomenal job that they do," he said.
Robert Richmond said although he would not normally play a grand piano outdoors the acoustics had been "absolutely perfect".
A grand piano has been carried to a point overlooking a Cumbrian lake to honour two climbers killed on Britain's highest mountain.