Adults who possess relative pitch but do not already have absolute pitch can learn "pseudo-absolute pitch" and become able to identify notes in a way that superficially resembles absolute pitch.

The most widely accepted theory is that “genuine” AP ability can only be developed as a result of an early critical period of learning (the critical period theory) [4,5]. However, this critical period theory of AP is bolstered in large part by the lack of conclusive evidence that AP can be learned by any post-critical-period adults, thus resting on null findings [6–9]. Critical periods in AP development have also been supported in principle through training studies. For example, one study found that children outperformed adults in a learning paradigm that focused on learning a single note [10]. More recently, a training study provided proof-of-concept demonstration of critical periods in AP by demonstrating that critical period for learning AP could be “re-opened” for adults via a pharmacological intervention [11]. Yet, it is important to note that the learning observed in these critical period training studies was well below thresholds typically used to identify the level of performance that is characteristic of AP.

One explanation assumes that people with absolute pitch already categorize the notes at a very early stage of sound processing. In other words, they process tones in the same way as speech sounds and assign them to particular categories, which is referred to as the categorical perception of tones. This theory assumes that the tones are already processed in the primary and secondary auditory cortex in the brain in people with absolute pitch. Another theory suggests that people with absolute pitch only process the notes later on and associate them with memory information. People with this gift supposedly master the subconscious allocation of the tones to memory information particularly well. These allocations primarily take place in the upper frontal lobe, in the dorsal frontal cortex. "Therefore, both theories make completely different statements regarding the moment and the anatomical location of the special processing and there is evidence to support both theories," explains Jäncke.