Upon retiring from Brown Memorial, Walker was given the title Minister of Music Emeritus in recognition of his distinguished service to the Baltimore church.

In 2013, he became interim organist and choirmaster at Grace and St. Peter's Church, an Anglo-Catholic Episcopal parish, conducting a professional choir of nine in a demanding program of choral masses, motets, and plainsong (September 2013–June 2014).

"[10] In addition to solo organ appearances, Walker often has performed with notable orchestras such as the San Francisco Symphony conducted by Michael Tilson Thomas.

Playing for a congregation "singing with its full heart and soul," he said, "is moving beyond measure...through the way I interpret the texts in the hymns...It's a combination of being an organist, a composer, and a pastor.

"[7] He told one magazine interviewer, "Service players create something meaningful and artistic by providing leadership in the liturgy, as well as congregational participation in worship.

[16] Shortly before he was to begin this series, the devastating 1999 Chi-Chi earthquake hit Taiwan on September 21 which measured 7.6 on the MMS scale.

Walker's performances became benefit concerts, instead helping to raise money for disaster relief between October 1999 and February 2000.

A recital by Walker, originally intended to be part of the 50th anniversary celebration of Taiwan's current government, was transformed into a memorial service for the earthquake's victims.