M-1 of Dead Prez performing at McPherson Square Park on Wednesday. (Chris Richards/TWP)

With a crowd of about 150 trying to squeeze beneath a makeshift canopy protecting them from the afternoon drizzle — white tarp, bamboo poles — rappers M-1 and stic.man delivered politically-charged rhymes over a not-so-powerful P.A. system that distorted their words into the sonic texture of an angry voice mail.

No matter. The duo’s message appeared to resonate more than the music, anyway. Couplets from the group’s 2008-election-era tune “Politrikkks” earned the afternoon’s biggest cheers after “Hip Hop,” the duo’s signature anthem from 2000 (the song’s wormy bass line might still be the best in the history of rap music).

M-1 spoke out against Walmart in Washington, the mass media, the prison industrial complex and addressed a litany of other issues. Both in song and between them, the group’s message felt like an ideal fit for a multi-faceted protest movement that’s still groping for a soundtrack.

Could it be hip-hop? Yesterday, Washington duo Thievery Corporation uploaded a video for its new pro-Occupy tune titled “Unified Tribes,” featuring rapper Mr. Lif. Much of the video was filmed — where else? — in McPherson Square.