When compact cassettes appeared in the 1960s they were not taken seriously by the professional world because of their very low grade quality. This was largely due to the very narrow tape tracks resulting in poor signal-to-noise ratios. Also the early cassette machines were often inferior in performance. Since then the tape and the machines have improved out of all recognition and while cassettes do not give the same quality as a full size (open reel) machine, and still less than digital recording, nevertheless their performance can be perfectly adequate for some professional purposes, such as speech. (But even so, very compact digital recorders are replacing cassette machines.) The general principles of cassettes and their machines are exactly the same as those of open reel machines and we shall not repeat them. It will be enough to give the important data about cassettes, starting with the track layout. Figure 16.1 shows how the tracks are arranged for cassette tape, while Figure 16.2 shows the layout for ‘quarter-inch’ tape.