There is a ton of information in the Dapper Manual online helping you to make Dapper so its job faster. Please check it out by clicking here.
Dapper scans each and every playlist you have in the “Dapper” folder in Music or iTunes app, to make sure it gets a link to each and every song and also tries to extract all the artwork for each of the albums it finds… Why not speed this up?
If you create a playlist named All Dapper Music inside the Dapper folder then Dapper will instead just use that playlist to build its music list, and ignore the rest until it’s time to save playlist files themselves. This can save you a ton of time in the “scanning” area, especially if you have a lot of overlap in your playlists.
When dapper is scanning, one of the things it does is to check for album artwork, and create an artwork image for each album, called folder.jpg, in the album directory.
If you have a lot of music with no artwork, Dapper will continuously try and see if it can extract it from the music files in that album. This can also slow down the initial scan, so you may want to make sure your music has album art associated to it or uncheck the box labelled “Collect album art and save to folder.jpg” in the Options tab of Dapper Settings.,