Hello Randy, et al.,
The short answer to your question is that the revision committee is interested in what you think is your best and most appropriate music for The Sacred Harp.
You should feel free to submit any tunes that are in keeping with the styles of music in The Sacred Harp. This could include easier and more challenging songs (though probably not songs that are more challenging than challenging songs in The Sacred Harp), major and minor tunes, short and long tunes (though, again, not tunes that are longer than the longer tunes in The Sacred Harp), plain and fuging tunes (not to mention tunes in other styles found in the book), tunes in any of the seven modes of time in The Sacred Harp, etc. The committee will acknowledge receipt of your submissions, and will review and sing through all music we receive.
All best,
Jesse