Participants performed a serial reaction time task, responding to either asterisks presented at varying screen locations or centrally presented letters. Stimulus presentation followed a fixed second-order conditional sequence. Each keypress in the experimental groups produced a contingent, key-specific tone effect. The critical variation concerned the mapping of tones to keys. In Experiment 1, keypresses in one control condition produced noncontingent tone effects, while in another control condition there were no tone effects. In Experiment 2, three different keytone mappings were compared to a control condition without tone effects. The results show that tone effects improve serial learning when they are mapped to the response keys contingently and in a highly compatible manner. The results are discussed with reference to an ideomotor mechanism of motor sequence acquisition.