Track-at-Once recording is what most recorders and software support today. Each time a track is finished, the recording laser is stopped, and two run-out blocks are written. When the laser is started again to write another track, one link block and four run-in blocks are written.
These blocks don't affect data tracks because you never read between data tracks, but they are a problem for audio because in some audio players you might hear a click when the link and run blocks are encountered between tracks. These link blocks may also cause problems if a disc is to be mastered and duplicated at the factory, and many disc replicators refuse or remaster Track-at-Once discs. For professional audio use, you need Disc-at-Once.
Note: Another cause of clicks between tracks is the CoolWave audio-editing shareware. It includes header information which is recorded as a click on CD-R. Use another editor, or check the Internet for patches to CoolWave which strip the header information.
In Disc-at-Once recording, all tracks are recorded without ever stopping the laser, and the disc is closed. Hence no link blocks and no clicks.
Disc-at-Once has only been added/available with the recent generation of CD recorders and recent firmware upgrades.
Note: Track-at-Once recording has nothing to do with the length of the gap of silence between audio tracks! Disc-at-Once recording is a prerequisite for being able to control the length of the gap (down to zero seconds), but it is not the only one. For the moment it is not possible to control the length of the gaps between tracks with any version of Easy-CD Pro.