Two performers, one man playing a guitar, and one woman with a mic raised to her mouth are sitting on chairs performing.
A man and a woman are performing a song together.
The two performers are a man and a woman and they are both performing, so they must be performing together.
If one man is playing a guitar and one woman has a mic to her mouth one can assume what they are performing is a song.
one man playing a guitar and one woman with a mic are performing a song together.