When it comes to describing music that is played "in slow tempo," there are a number of synonyms that can be used to convey this idea. Some options might include "at a leisurely pace," "with a relaxed tempo," "slowly and steadily," or simply "at a slow tempo." Additionally, you might describe the pace of the music as "languid," "deliberate," or "sluggish." Ultimately, the specific language you choose will depend on the type of music you are discussing, as well as the tone and mood you are looking to convey through your descriptions.