Commentary on Psalms 138

Maschil--(See on Psa 32:1, title). When he was in the cave--either of Adullam (Sa1 22:1), or En-gedi (Sa1 24:3). This does not mean that the Psalm was composed in the cave, but that the precarious mode of life, of which his refuge in caves was a striking illustration, occasioned the complaint, which constitutes the first part of the Psalm and furnishes the reason for the prayer with which it concludes, and which, as the prominent characteristic, gives its name. (Psa 142:1-7)

with my voice--audibly, because earnestly.