Severus Snape plays the ukelele. He felt he had to select at least one of the instruments the older students in Slytherin thought so terribly elegant, and the ukelele was 1) affordable and 2) portable. He considered a banjolele (a banjo the size of a ukelele), but Narcissa threatened to throw him into Black Lake if he got one.
She taught him piano because she thought the older students were ridiculous and easily taken in.
(The mania for the accordion, crumhorn, banjo, etc. only started when an upper class muggleborn in the early 1900s managed to convince the population of Slytherin that of course those instruments were the last word in elegance. Why, the Prince himself plays the banjo!)
(The Prince did not play the banjo)
In any case, the ukelele let him fit in with some of the other Slytherins and had some added benefits.
To whit: it was very easy to accompany yourself while singing. Especially the songs of the 1920s and 1930s, which delighted his Nan.
Narcissa found less delight in his newfound hobby, mostly because he sang things like I Want to Be Bad, Making Whoopee, Let’s Misbehave, and I’m a Bear in a Lady’s Boudoir.
Severus became intimately familiar with her silencing and stinging hexes. She could identify any of those songs by the first few notes, like an especially nerve-wracking parlor game.
Her Slytherin Musical Evenings were never quite the same once Severus discovered the ukelele.
(Of course she hosted Musical Evenings. Slytherin House was a microcosm of the Society over which she would eventually reign. She also hosted teas, afternoon dances, and the occasional picnic. No one quite knew how she managed so many Outstandings on her OWLs and NEWTs since she seemed to spend more time event planning than studying.)