Jerry Troxell's Riff Rap was commissioned by the Chicago Chapter of ASTA in 1990. The continuous rhythmic texture serves as the foreground initially, then as background for the soloists. The piece is an intriguing blend of old (concerto grosso format) and new (rap-like rhythmic ostinatos). Ensemble parts are playable in first position and solo violin goes to third. Rhythms are very challenging but fall into regular patterns.