Early on, Queen toured as a power trio (bass, drums and electric guitar), but that gradually changed as more piano-based material was introduced to their albums, including some of their hit singles. Between February and May 1974, they'd depend on if local promoters or concert organisers could supply them with a piano; if they didn't, then those concerts would do away with White Queen and Seven Seas of Rhye. From October 1974 until August 1986, they always had an acoustic piano on stage. After Mercury's death, they rarely did, instead relying on digital keyboards imitating a piano sound (notable exceptions were Pavarotti and Friends in 2004, as well as the QPR tours in 2006 and 2008, when Paul Rodgers played a baby-grand one on the song Bad Company).
Between October 1974 and September 1976, they'd rely on what could be rented at each venue. For the A Day at the Races tour, they borrowed a Steinway owned by Elton John, which was then lost when the truck had an accident in Chicago due to a snowstorm so the crew had to swiftly hire another one; Mercury finally bought another Steinway (a 1972 D concert grand model made in New York) and used it for every single concert from November 1977 onwards. After his death, the company offered to restore it (imagine all the wear and tear from being on the road for almost a decade), and it now lives in Brian's lounge.
Despite having used synthesisers on both of their 1980 albums, they weren't incorporated to the stage act initially, and in fact when they played Flash's Theme for the first time on the 6th of December that year, they did it with Brian playing guitar all along. It didn't work too well for them, so from the next concert onwards he played it on piano, switching to a synthesiser for the main hook. The synth was placed on top of the piano just for that song. A few more synth-based tracks were added to the set in 1981, and from 1982 onwards they had an auxiliary keyboardist with an ever-growing synth rack. The main electric or electronic keyboards they used on stage were:
From 2005 onwards they mostly endorsed Korg products, including a CX-3 organ, two Triton Extreme LE's, M3 88 (from 2008 onwards) and a microKorg.