Final answer:
To "tune up" something means to adjust it to a desired pitch or frequency, often by comparing it with a reference frequency and making adjustments until the desired sound is achieved.
Step-by-step explanation:
To "tune up" something means to adjust it to a desired pitch or frequency. For example, piano tuners listen for beats when comparing a note with a tuning fork, and they adjust the piano strings until the beats disappear. They use trial and error to fine-tune the instrument, making adjustments and testing the pitch again. Tuning forks are also commonly used by musicians to tune other musical instruments.