In modern times, well temperaments have been replaced by equal temperament, so much so in Western music that equal temperament is considered standard tuning even for voice and for instruments that are more likely to play using just intonation when they can (see above). In equal temperament, only octaves are pure intervals. The octave is divided into twelve equally spaced half steps, and all other intervals are measured in half steps. This gives, for example, a fifth that is a bit smaller than a pure fifth, and a major third (Major and Minor Intervals) that is larger than the pure major third. The differences are smaller than the wolf tones found in other tuning systems, but they are still there.
Equal temperament is well suited to music that changes key often, is very chromatic, or is harmonically complex. It is also the obvious choice for atonal music that steers away from identification with any key or tonality at all. Equal temperament has a clear scientific/mathematical basis, is very straightforward, does not require retuning for key changes, and is unquestioningly accepted by most people. However, because of the lack of pure intervals, some musicians find it unsatisfying. As mentioned above, just intonation is sometimes substituted for equal temperament when practical. Some musicians would also like to reintroduce well temperaments, at least for performances of the music which was written for well-tempered instruments.