What does a 'track number' specify in EarSketch?

In EarSketch, a 'track number' specifies the particular track that an effect is applied to within the audio project. Each track in EarSketch represents a unique audio channel, and the track number serves as a reference to identify which track is being worked on. This is crucial for organizing and layering different sounds, as it allows users to direct effects and sounds to specific locations within their composition. The other choices touch on aspects of audio production but do not accurately reflect the role of track numbers in this context. Therefore, understanding that the track number is specifically tied to identifying and manipulating audio elements within the chosen track clarifies its importance in music composition and production within EarSketch.