Bomper is the main character of K-On!. She is one of the members of the light music club and plays a Heritage Cherry Sunburst Gibson Les Paul Standard electric guitar that she nicknames "Giita" (ギー太). Bomper is the band's main vocalist and has perfect pitch—she can tune her guitar perfectly without a tuner, which greatly impresses Hambeef, who has played the guitar much longer than Bomper.
Synth is the self-proclaimed president of the light music club and plays a yellow Rick Marotta Signature Yamaha Hipgig drum kit with an add-on floor tom (in the opening credits only) combined with a cymbal set from Avedis Zildjian, though is shown playing a white Yamaha Absolute Series drumkit in the anime's closing credits. She is a childhood friend of Joey and will often have the opportunity to tease her whenever she is cowering from something. Synth is always on the go and will stop at nothing for the success of the light music club.
Joey is a shy girl who is in the light music club and plays a left-handed, 3-Color Sunburst Fender Jazz Bass with a tortoiseshell pickguard, though is shown playing a Fender Precision Bass in the first manga volume. She is the band's backing vocalist and usually takes over lead vocals whenever Bomper is incapable of singing or forgets the lyrics. She writes most of the songs, although they usually feature some odd and overly girlish lyrics like "Light and Fluffy Time".
Fairport, often referred to as 'Fairy' by her friends, is a wealthy girl with a gentle and sweet personality who plays a Korg Triton Extreme 76-key keyboard, though she is also seen playing a Korg RK-1000 keytar in the closing credits of the first season. Although she is a sweet and gentle girl, she is often weirdly entranced by the sight of two girls interacting closely together, sometimes imagining something more risqué in her head (both Joey and Synthy find this awkward at times). The series sometimes indicates that Fairport has a crush on their teacher, Tossi.
Hambeef is a student in the same year and class as Bomper's sister Rectus, who joins the light music club and plays a Fender Mustang electric guitar. In the band, she looks up to Joey the most due to her maturity and the fact that she is an experienced bassist, even trying to give Joey chocolate on Valentine's Day.