aspiration, breath, breathy voice, exhalation, little voice, low voice, mumble, mumbling, murmur, murmuration, murmuring, mutter, muttering, sigh, soft voice, stage whisper, still small voice, susurration, susurrus, underbreath, undertone, whisper, whispering

abjectly, anticipatingly, anticipatively, anticipatorily, anxious, apprehensive, apprehensively, aside, bashfully, behind the curtain, behind the scenes, behind the veil, between the teeth, covertly, diffidently, expectantly, expectingly, fearfully, for fear of, hopefully, humbly, in a corner, in a whisper, in an aside, in darkness, in hidlings, in secret, in suspense, in the background, in the dark, keyed-up, meekly, modestly, mousily, nobody the wiser, on all fours, on bended knee, on edge, on tenterhooks, on tiptoe, out of earshot, quakingly, quivering, secretly, shrinkingly, shyly, sotto voce, sub rosa, submissively, taut, tense, timidly, timorously, tremblingly, tremulously, under the breath, under the rose, undercover, underground, with breathless expectation, with due deference, with muscles tense