“We are using a simple program to burn audio discs. We’re able to make them okay, but are confused about some of the options. When making an audio CDR or CD-RW we have the option to leave the session open and append later, but the results of trying this have been unsuccessful. What’s wrong?”
All CDR and CD-RW discs can be written in such a way that more information can be added later. When you add more it just picks up where it left off and appends the new information. From the very beginning most audio CD recorders have been able to make discs this way. “Finalizing,” as it has sometimes been called in the CD recorder world, is a process done at the end to close out a disc. At that point three things happen: 1) The table of contents (TOC) is written; 2) No more data can be written to the disc (at least not in such a way that it can be used); 3) If it’s an audio disc it now becomes readable on most CD players. An unfinalized disc can be read on some pro players that have the capability, but in general aren’t suitable for public consumption yet. This was always a handy feature because it allowed users to have “work discs” where more material could be added on an ad hoc basis (keep in mind blank CDR media used to cost $60 or more each).
If you do leave a disc unfinished you can go back later and add more data (this is true of audio and data CD’s). The ultimate behavior of that disc on other systems will depend on a variety of factors that we don’t have space here to get deeply in to. For example, if you intend to send an audio disc to a CD pressing plant for mass production it really needs to be written in what is known as disc-at-once, which basically means the whole disc is burned in one pass of the laser. When the laser turns off and back on (for any reason) in the middle of a disc it creates errors. These don’t normally effect playback, but they will show up as fatal flaws at the manufacturing plant, requiring a new master disc to be made. Likewise data discs can be burned as multisession discs. Under the proper conditions these will show up on a computer as several discrete volumes. The problem is sometimes the computer’s CD ROM drivers don’t recognize the multisession nature of the disc and only the first volume mounts.
The bottom line is: unless you really need to make a disc in stages you are ultimately better off to just burn a disc in its entirety (especially audio discs). CDR media is so cheap now this isn’t as wasteful as it once was, and with CD-RW media you can erase and start over at your discretion. That said, burning in steps can often be done without any major problems depending upon what you intend to do with it.
