Schroeder's most recognizable trait, is probably his toy piano, which he often plays.
On September 24, 1951, Charlie Brown introduces Schroeder to a toy piano. He tells Schroeder it is easy to play it, then shows him by hitting a few notes. Then Schroeder plays a real song, leaving Charlie Brown blushing. Ever since then, Schroeder has had his toy piano.
In the strip from October 2, 1951, Charlie Brown attempts to get Schroeder to play a real piano, but only succeeds in making Schroeder cry. Similarly, in the December 13, 1953 strip, Violet eventually manages to convince a nervous Schroeder to play his toy piano whilst seated in front of her mother's real piano.
The piano's capability is illustrated in 1965's A Charlie Brown Christmas. Lucy asks Schroeder to play "Jingle Bells". Schroeder plays it in the style of a conventional piano, then manages to generate the warm tones of a Hammond organ, but Lucy cannot recognize the tune until the now-irritated Schroeder plays it, off-key with one finger, in the tones of a normal toy piano. It's the only time in the history of the television specials that his toy piano ever actually sounds like a toy piano, with 'plinking' sounds. In 1966's It's the Great Pumpkin, Charlie Brown, Schroeder accommodates Snoopy (who was dressed in his World War I Flying Ace outfit) by playing a brief medley of World War I songs at Violet's Halloween Party; such as "Pack up Your Troubles in Your Old Kit Bag", "Roses of Picardy", and others.
Schroeder is normally a very passive character, content to play his music, but he can be angered quite easily, especially if his music or his idol Beethoven are insulted. In one short, Lucy points out to him the woefully inadequate single-octave range of a toy piano; an angry Schroeder yanks it out from under, causing her to conk her head on the floor. This became a frequent running gag in the strip's later years. On another occasion, Lucy asked if pianists make a lot of money, and Schroeder flew into a rage: "Who cares about money?! This is art, you blockhead! This is great music I'm playing, and playing great music is an art! Do you hear me? An art! Art! Art! Art! Art! Art!" (the last five words punctuated by slamming his hands against his piano). However, when Lucy asks the same question in the movie A Boy Named Charlie Brown, Schroeder admits: "Some do, if they practice real hard, I guess." In the Charlie Brown Christmas special, Lucy tells Schroeder that Beethoven "wasn't so great". When Schroeder defensively demands an explanation, Lucy replies that Beethoven has never been on a bubble gum card and that one cannot be considered great without appearing on one.
The musical notes Schroeder plays also seem to have substance; characters are able to touch them as they appear in the air. Snoopy, for example, once takes a handful of them, and roasts them over a campfire, and has on at least one occasion been seen dancing atop the musical staff containing the notes. And starting on October 9, 1989, the notes started falling off Schroeder's piano (although Snoopy always tries putting them back on).
Lucy has often spoken of getting Schroeder to give up his piano, such as getting him to realize that married life has financial hardships and he may have to sell his piano in order to buy her a good set of saucepans. On two occasions, Lucy went so far as to destroy Schroeder's piano in an attempt to be rid of the "competition" for his affection, but all attempts failed:
- In a series of strips from January 1969, Lucy throws the piano into a tree, which is later discovered to be none other than a dreaded Kite-Eating Tree, which evidently doesn't distinguish between kites and toy pianos. When Schroeder orders a replacement in the strip from February 1, 1969, Charlie Brown asks if his piano was covered by insurance, to which Schroeder replies, "How do you explain to the insurance company that your piano was eaten by a tree?".
- In her second attempt, from an October 1974 strip series, Lucy throws the piano into the sewer, from which Charlie Brown and Schroeder attempt to retrieve it. Schroeder is able to reach it, but it gets stuck, and then when it starts raining heavily the piano gets washed out to sea.
- Another time Lucy destroys both his piano and his bust of Beethoven; Schroeder calmly picks out a new piano and bust from a closet well-stocked with duplicate pianos and busts.
One instance in which the piano is destroyed accidentally is in a series of strips from April 1986. A cannonball, fired by Snoopy and his bird friends (acting as legionnaires trying to retake Fort Zinderneuf), ends up landing on the piano and crushing it.