[3] In the late 1980s, he and Irish fiddler Martin Hayes formed a band in Chicago called Midnight Court, which combined traditional music with rock and roll.

After its demise, Cahill and Hayes continued to work together and formed an acoustic duo in 1996, developing an "unrushed, lyrical, highly expressive interpretation" of traditional Irish music.

[6] In 1999, a New York Times reviewer described Hayes and Cahill's approach as "stripping old reels and jigs to their essence, leaving space between the notes for harmonics and whispered blue notes," resulting in "a Celtic complement to Steve Reich's quartets or Miles Davis's Sketches of Spain.

"[7] They toured extensively and released three recordings on the Green Linnet label: The Lonesome Touch (1997), Live in Seattle (1999), and Welcome Here Again (2008).

[8] Cahill and Hayes, along with singer Iarla Ó Lionáird, fiddler Caoimhín Ó Raghallaigh and pianist Doveman, were the members of The Gloaming, an Irish-American supergroup whose first album was released in 2014, winning the Meteor Choice Music Prize for Irish album of the year.