Yea, the creators of Braid didn't make their own music, they just licensed it. Check their stuff out at last.fm or something. The songs are:
“Maenam”, by Jami Sieber, from the album Hidden Sky.
“Undercurrent” and “The Darkening Ground”, by Jami Sieber, from the album Lush Mechanique.
“Tell It By Heart” and “Long Past Gone”, by Jami Sieber, from the album Second Sight.
“Downstream”, by Shira Kammen, from the album Music of Waters.
“Lullaby Set”, by Shira Kammen and Swan, from the album Wild Wood.
“Romanesca”, by Cheryl Ann Fulton, from the album The Once and Future Harp.