Wonder Girls

The debut single that first imprinted the five members' chemistry and harmonies on the public.

• The synth sound of the intro and the drum-machine beat typify the girl-group dance track of the mid-2000s.
• In the pre-chorus (the short passage that builds tension just before the chorus), stacked harmony vocals (chorus overdubs) anchor the song.
• The rap was handled by Hyuna, a member of the debut lineup, and the song captures the group before its identity had fully taken shape.
• Though it drew little attention, the song is regarded as having proven the five members' harmonies and the precision of their group choreography.

A song in which retro synth-pop and simple choreography combined to set off a nationwide craze.

• The simple synthesizer riff (a short, repeated melody) of the intro carries straight through as the hook that dominates the entire song.
• In the chorus, the repeated title phrase locks precisely with the signature hand-waving move, so the choreography itself makes the structure of the chorus visible.
• The 1980s disco-style synth sound is said to have been a deliberate choice of retro texture over the polished production then in vogue.
• The sight of the audience joining in the choreography during the performance is counted among the iconic moments of late-2000s music shows.

A song that revived the 1960s Motown sound, climbed all the way to Billboard and captures the group at its peak.

• From the intro onward, a brass-flavored arrangement and a clap (handclap) rhythm evoking the sound of 1960s American Motown girl groups create a retro atmosphere.
• In the chorus, the signature move of thrusting the arms forward and pulling them back falls exactly on the beat where the title phrase repeats, making the song's structure visible to the eye.
• The arrangement, built from short lines traded among the members, is credited with highlighting the blend of the group's voices.
• The English version reached the Billboard Hot 100 in 2009, standing as proof that a retro sound could resonate with American listeners too.

A song loved the same year for an urbane concept that contrasted with the group's retro image.

• Laying sunglasses-clad, urbane choreography over a hip-hop beat, it deliberately contrasted with the gentle retro image of "Tell Me" and "Nobody."
• The short, punchy hook of the chorus shows the typical late-2000s K-pop arrangement, designed for repeated exposure on broadcast chart shows.
• Yubin's rap part, with a flow pressed tightly onto the beat, marked a turning point in establishing a stronger presence as the group's rapper.

A collaboration with Akon whose sound openly carries the group's ambitions for the American market.

• The 808 bass (an electronic bass drum that emphasizes the low end) characteristic of American R&B·hip-hop production, along with a beat that makes use of empty space, gives it a texture unlike their earlier songs.
• The verses (stanzas) traded with Akon show Wonder Girls stepping away from chorus-driven songs made for the domestic market to try an American song structure.
• With a higher proportion of English lyrics than Korean, the song makes its aim at the American market clear from the sound alone.

The comeback song that announced the regrouping after 5 years and opened the band era.

• Its bright, tropical sound built on synth-pop serves as a prelude announcing the change in a group long absent.
• The vocal split, with four members trading lines, is credited with turning the smaller lineup of the time into a natural strength.
• The light synth hook in the chorus gave up the striking point choreography of earlier years and chose to catch the ear through the vocals and harmonies themselves.

The song that completed the transformation into a band; it topped the charts right after release and was loved for a long time.

• The offbeat (a technique that accents the weak parts of the beat) guitar chops typical of reggae·ska rhythms create the groove that governs the whole song.
• On stages where the members played their own instruments, Sunmi's bass, Yeeun's keyboards, Yubin's drums and Hyerim's guitar were laid bare, making for a rare idol stage where the structure of the arrangement could be seen.
• The languid vocal tone of the chorus and the space between it and the rhythm gave the song a texture well suited to repeated summer radio play, and this is cited as the reason it stayed on the charts long after release.
• Staging that focused on playing and the groove itself rather than choreography is regarded as the moment the group clearly broke from its past image built on point choreography.