Observational data and geochronology show synchronous deformation, metamorphism and intrusion of granite in many obliquely convergent (transpressive) orogenic belts. In these belts, melt extraction and transport was by syntectonic pulsed flow in structurally-controlled channels through migmatites, and granite plutons were constructed by aggregation of multiple melt batches. Compositional information in the granites provides clues to unraveling the petrological processes by which their parental magmas were generated and extracted from the crust, but we need to read the information with sufficient insight to enable prudent interpretation, because we cannot see granite in process of formation! In this paper, we evaluate the role of source processes in granite petrogenesis using results from west-central Maine, in the northern part of the Appalachian orogenic belt of eastern North America. In this area, precise U-Pb zircon/monazite crystallization ages of schlieric granite in migmatite, metric to decametric sheets of granite and kilometric granite plutons are in the range c. 408-404 Ma, within 1 Ma at 95% confidence limits, and in one granite, the Phillips pluton, multiple samples of leucogranite and granodiorite yield synchronous ages. If the results of this study are representative, they suggest that in restricted segments of orogenic belts regionally-significant crustal melting in nature occurs within short timescales (~ 107a), and melt extraction and transport, and pluton construction are fast processes. In the Phillips pluton, petrographic features and geochemistry of leucogranite samples, including K2O contents, RbSr ratios, covariation in Rb, Sr and Ba distributions, and chondritenormalized REE patterns, are inconsistent with fractional crystallization, but compatible with eutectic high-to-moderate a(H2O) muscovite-dehydration melting of a predominantly pelite source. Petrographic features and geochemistry of granodiorite samples, including chondrite-normalized REE patterns and RbSr ratios, also suggest derivation from a metasedimentary source, but by non-eutectic (minimum) moderate-to-low a(H2O) biotite-dehydration melting of greywacke. In this pluton, the two types of granite s.l. show heterogeneity in Nd isotope compositions (granodiorite εNd (404 Ma) of + 0.1 – −1.8; leucogranite εNd (404 Ma) of −5.3 –−8.0), which we interpret to reflect derivation of the two granites from isotopically-distinct sources, to preserve withinsource heterogeneity and to imply efficient extraction, ascent and emplacement of melt without significant interaction between individual batches.