As you know, most multitrack recordings are mixed to DAT these days, but at a professional level, DAT isn't always considered to be entirely satisfactory. For one thing it is only 16 bit, which means that its sound quality isn't any better than the CD people will listen to at home. The engineer therefore has absolutely no headroom to play with, and inevitably there is a margin of unused capability that makes the recording not quite as good technically as it ought to be. It won't be too long before we see 20 or even 24 bit stereo formats in the studio on a regular basis, although it might be some years before any one is accepted as a standard. In the meantime, many producers are opting for the 'old fashioned' alternative of analogue reel to reel tape. They don't used a battered old Revox however. Top studios will have a slightly worn but well maintained Ampex or Studer stereo machine that runs at a speed of 30 inches per second (twice the 15 ips long considered the professional norm) and takes half inch rather than quarter inch tape. Such a machine isn't totally transparent but has a definite sound of its own, and it's a sound that producers like, particularly if a recording has been made on a digital rather than analogue multitrack. The frequency response is in fact better than DAT or CD which can only manage around 20kHz at the top end. Half inch analogue at 30 ips can go up to 25kHz and beyond, and quiet signals can still be clearly heard below the already low noise floor - even without Dolby SR noise reduction. There are many who will say that half inch is better than digital for these reasons, and so many successful records have been mixed to half inch that it is very difficult to disagree.
When the stereo master is finished, then the producer's work still continues into the CD mastering studio. This is the very final stage where the stereo master is committed to a U-Matic video tape or Exabyte data cartridge. After this, no further alterations can be made to the sound. CD mastering isn't quite such a creative opportunity as vinyl mastering used to be (mostly because of the technical limitations of the vinyl medium), and still is on occasion. It is however a chance to make sure that all the tracks have the right relative levels, EQing and compressing where necessary. You will also set the length of the gaps between tracks, and perform any crossfades between tracks that you think are appropriate (and to hell with radio plays!).
When you leave the CD mastering studio your work as producer is complete and you can look forward to the financial rewards for your labours. Actually, you may also have to look forward to your recording being handed over to specialist remixers - a fact of life that you will accept as gracefully as a true professional would!