High proficiency in L2 partly depends on acquiring many formulaic sequences (FSs), yet post-childhood learners find this difficult. Ways of accelerating the acquisition of FSs would be welcome. Small-scale studies have indicated that assonance (e.g., strong bond) makes studied FSs especially retrievable if, during exposure, assonance is made the object of teacher-instigated awareness-raising and attention direction. However, questions remain about effect size and duration. In two new experiments a mnemonic effect of assonance was detected after 5–10 minutes. This was despite a sorting task thought likely to direct participants’ attention particularly to the control collocations. The effect appeared to fade over an hour and disappear after a day. A small-scale meta-analysis indicates the effect is initially of medium size. It is discussed how short-term operations of such an effect could facilitate the fuller acquisition of partly learned assonant FSs. The study proposes avenues for research into means whereby the mnemonic effect of assonance might be exploited in learning materials. This touches on effects of item frequency, mutual information, and concreteness-imageability of meaning.