Agree on form and tuning first
Both players should know the sounding key, section order, and number of measures in each repeated phrase. Confirm each instrument's tuning, particularly if one has low G or is a baritone. The same physical shape may not produce the same chord across different tunings. Play the opening progression together slowly and settle any disagreement about timing or harmony. A shared AudioChords reference can help with orientation, but both players should verify the musical changes rather than assuming the screen resolves every arrangement decision.
Give the parts different jobs
Let one player maintain a restrained strum while the other uses sparse picked notes or a higher voicing. The second part can answer the voice between phrases rather than sounding continuously. If both instruments occupy a similar register, rhythmic separation becomes especially useful. Try having one sustain while the other moves, then exchange roles in a later section. Keep important chord arrivals aligned even when the internal rhythms differ. The aim is a conversation between parts, not two complete solo arrangements competing for the same space.
Listen from outside the performance
Record a verse and chorus, then listen together without playing. Identify moments when both parts accent the same weak subdivision unintentionally or when a fill masks the singer. Remove one event and compare the result before adding anything new. Agree on a visible cue for the ending and rehearse the final release. You can create a larger chorus by changing only one part, allowing the other to remain an anchor. A strong duet uses the similarity of the instruments for blend while preserving enough contrast that each player's contribution has a clear purpose in the phrase.