There are various synonyms that can be used in place of the phrase "singing same old song." Some options include "repeating the same old tune," "recycling the same old melody," "echoing the same old chorus," "regurgitating the same old refrain," or "playing the same old notes." All of these phrases convey a sense of monotony and predictability, as if someone is stuck in a rut and unable to come up with anything new. They can be used to describe situations where people are stuck in the past or failing to innovate, whether it's in music, business, or personal relationships.