When you direct your sims to work on skill building, have them do it in a room that has a radio. Then turn the radio on.
In the martial arts academy in Shang Simla, there’s a stereo in the upstairs workout room, so I’ll usually send my sims there to get started building this skill.
Sims that are in a room with music playing get a positive Enjoying Music moodlet to go along with whatever they are doing at the time.
Setting the radio to my sim’s favorite channel will usually increase the moodlet’s effect, and the sim’s preference will often dictate what channel the radio is set to when she turns on the radio autonomously.