In addition to Mf18M and Drumming, which have been suggested by others, I'd also add Six Marimbas/Pianos, Four Organs, and in particular Music for Mallet Instru

In addition to Mf18M and Drumming, which have been suggested by others, I'd also add Six Marimbas/Pianos, Four Organs, and in particular Music for Mallet Instruments, Voices, and Organ, as Steve Reich pieces that I happen to enjoy more than the ones you enjoy :-) Mf18M and MfMIVO always put me in a very contemplative mood. And for anybody reading who might be interested in other pieces of minimalistic music, I might recommend - Hallelujah Junction - John Adams - Common Tones in Simple Time - John Adams - Harmonliehre - John Adams - Nixon in China - John Adams - The Dharma at Big Sur - John Adams - Music for Blocks of Wood - Steve Reich - I am Sitting in a Room - Alvin Lucier (particularly the extended version) - Glassworks - Phillip Glass - Music in Twelve Parts - Phillip Glass - Metamorphosis - Phillip Glass - Phillip Glass Buys a Loaf of Bread - David Ives