jimlauI am physically unable to play an instrument or MIDI keyboard and capture the pitches. I'm just looking for a way to get the monophonic melody into my DAW. I tried forceful, punchy syllables. The timing aspect is pretty good, but the pitches can be way off, sometimes by octaves.
Even the best trained singer's can't reach notes outside their range, sopranos can't sing bass and that's an end to it. So being off by octaves isn't surprising. And the human voice actually isn't that good at sustaining a consistent pitch or producing perfect and consistently clear transients, which can throw audio to MIDI software.
You might find Jam Origin's guitar to MIDI software worth trying. It's intended for guitar (obviously) but can handle any audio source and can cope better than most with things like pitch bends and vibrato. Though shifting pitches around octaves is still likely to be needed. Or switching a synth's oscillators from e.g. 8 foot to 16 or 32 foot which will drop the pitch by one or two octaves.
You might find Sonar's step sequencer or a more advanced MIDI-capable hardware step sequencer useful as a creative tool. They have limitations, but can be a good way to create patterns and lines relatively easily and quickly without requiring the dexterity of a skilled keyboard player.
If you don't mind me asking, is your inability to play an instrument related to disability in any way? If so, it might help the collective mind to come up with useful ideas if we knew in what way.