The Rockport Celtic Festival at the Shalin-Liu Performance Center (Sept. 14-17) is geared toward exploring the similarities as well as the differences between music traditions, Irish and otherwise, that have become associated with The festival, now in its fourth year, has joined the impressive suite of annual events bearing the imprint of WGBH broadcaster Brian O’Donovan, whose long-running “A Celtic Sojourn” radio show formed the basis for the Christmas and St. Patrick’s Day “Celtic Sojourn” stage productions.

O’Donovan has long had a fascination with delving into the “roots and branches” of Celtic music, and the connections that bind songs, tunes, and styles associated with the Irish, Scottish, Cape Breton, English, and American folk traditions, as well as those of maritime Canada, Quebec, France (Breton), Spain (Galicia), even Scandinavia. Like its forbears, the Rockport Celtic Festival — now a joint effort by O’Donovan and his co-artistic director, Scottish harpist/vocalist Maeve Gilchrist — offers audiences an invitation to listen with discerning ears and open minds, all the while enjoying music, song, dance, and storytelling from top-rank performers.

The theme of this year’s festival centers on music associated with the French diaspora of Eastern Canada. Among the featured performers will be Quebecois trio Genticorum; Newfoundland-born singer and guitarist Matthew Byrne; Cape Breton fiddle-piano duo Kimberley Fraser and Troy MacGillivray — all of whom will be part of the festival’s official opening night concert on Sept. 15, along with Irish singer Éilís Kennedy and the duo of Allison de Groot and Tatiana Hargreaves, who bring a 21st-century sensibility to old-time American banjo and fiddle music.

But that’s only one night, and only part of the roster. Others who’ll be showing up at Rockport include multi-instrumentalist Seamus Egan – a long-time mainstay of “Christmas Celtic Sojourn”; Swedish fiddler Lena Jonsson, who brings her native music tradition into Americana/old-timey, bluegrass, rock, pop, and jazz; Shetland fiddler Kevin Henderson (Nordic Fiddlers Bloc, Boys of the Lough, Fiddlers’ Bid); acclaimed young fingerstyle guitarist Yasmin Williams; New York City-based guitarist, composer, and improviser Kyle Sanna, who has worked with the likes of Martin Hayes, Seamus Egan, Yo-Yo Ma, Béla Fleck, and Palaver Strings.

There’ll also be a contingent of Boston and New England performers, such as guitarist Conor Hearn – he’ll be performing with violinist Maura Shawn Scanlan as the duo Rakish at the Sept. 14 “festival club,” in addition to other collaborations; Scottish/Cape Breton-style fiddler Katie McNally, and legendary maritime singer David Coffin.

The festival’s other event include a post-opening night concert ceilidh (yes, there’ll be dancing) hosted by McNally, Henderson, and Hearn; a salon session with Byrne, Kennedy, and de Groot/Hargreaves hosted by Gilchrist; an hour of poetry, prose and music with O’Donovan, Gilchrist, and several performers; and the climactic “Letters from the Sea” – a selection of songs written by Kennedy based on letters she found in the New Bedford Whaling Museum, which served as the basis for her “So Ends This Day” album.

The festival website is rockportmusic.org/rockport-celtic-festival.