• Memory
• Associative learning
• Memory Retrieval
• Cognitive neuroscience
• Music

The effects of background music on learning and memory formation are inconsistent, partly due to the diversity of musical styles and inherent components, as well as variability in music perception and affinity. By stripping down musical harmony to its building blocks, namely discrete chords, we explored their effects on learning and memory retrieval of new word-image pairs. Chords, defined as two or more simultaneously played notes, vary in the number of tones and inter-tone intervals, yielding varying degrees of harmonic complexity, which translate into a continuum of consonance to dissonance percepts. In the current study, 50 participants heard four different types of musical chords (major, minor, medium complex, and highly complex chords) while they learned new word-image pairs of a foreign language. One day later, their memory for the word-image pairs was tested, along with a chord rating session, in which they were required to assess the musical chords in terms of valence, tension, and attention. A separate eye-tracking experiment was conducted, suggesting that highly complex chords tend to enhance pupil dilation. We found that musical chords containing dissonant elements were associated with higher memory performance for the word-image pairs compared with low-complexity chords. Moreover, we found that tension positively mediated the relationship between roughness (a key feature of complexity) and memory, while enhanced valence negatively mediated this relationship. The reported findings are discussed in light of the effects that basic musical features have on emotional responses and attention, in turn affecting cognitive processes of associative learning.