In a double, where two constrictions are available, improved cylinder and modified are a good pairing, especially in fixed-choke guns. If screw-in chokes are an option, try a more forgiving match, like skeet and light modified. Shoot the more open barrel first on the covey rise, then the tighter barrel as the birds make their escape.
The CD and DVD have a single track of data in the form of a spiral, which starts as the center going outwards. The data is stored on the bumps or pits which are then read by the CD/DVD layer. The bumps/pits on a DVD are much smaller than on CD, allowing the DVD to store more data.
A DVD (Digital Versatile Disc) is a disc that is able to store large amounts of information on a single disc. Higher resolution video can be running in the background while karaoke music is playing. This format is different from CDGs so you will need a karaoke player capable of reading DVDs to play this format.