A data payload PD is recorded on a compact disc in a format including a lead-in indicating a track start address ATOC and a subchannel P which changes state at a payload start address AP, subsequent to the track start address ATOC. Data ED recorded at the track start address ATOC includes unrecoverable data. Where the data payload PD is an audio track, an audio-only player begins to search sequentially from the track start address ATOC until the subchannel changes state, and reproduces the audio track from that point. A data player, on the other hand, begins to reproduce data from the track start address ATOC. When the unrecoverable data is read, the read operation is aborted, as it appears that the data has been corrupted. This operation cannot be easily circumvented, because it is not normally acceptable to ignore corrupt CD-ROM data. The disc may also include a second session containing an encrypted version of the data payload PD, where each sector is encrypted using a different key which is derived from a sector address by an algorithm and requires a special player program which performs the decryption. A supervisory program prevents circumvention of the copy protection.