Related Clues:

• Working together
• 'Merrily, we roll ___'
• Accompanying
• In tow
• Word with sing or string
• Beside
• Lengthwise
• In accompaniment
• 'Git ___ Little Dogies'
• Parallel to
• "Sing ___ With Mitch"
• See 66-Across
• On board
• By the way
• 'I knew it all ___!'