  Excerpts are widely used to preview and promote musical works. Effective
excerpts induce consumption of the source musical work and thus generate
revenue. Yet, what makes an excerpt effective remains unexplored. We leverage a
policy change by Apple that generates quasi-exogenous variation in the excerpts
of songs in the iTunes Music Store to estimate that having a 60 second longer
excerpt increases songs' unique monthly listeners by 5.4% on average, by 9.7%
for lesser known songs, and by 11.1% for lesser known artists. This is
comparable to the impact of being featured on the Spotify Global Top 50
playlist. We develop measures of musical repetition and unpredictability to
examine information provision as a mechanism, and find that the
demand-enhancing effect of longer excerpts is suppressed when they are
repetitive, too predictable, or too unpredictable. Our findings support
platforms' adoption of longer excerpts to improve content discovery and our
measures can help inform excerpt selection in practice.
