I was serious about the kazoo comment. It's a strong, consistent signal...admittedly not very expressive, but you can tweak that with editing and automation. Probably your best bet would be an electric one, like this model.
 
If you have mobility with your feet and legs, another option is using a set of organ bass pedals, like the StudioLogic MP-113. There are quite a few inexpensive DIY MIDI bass pedal projects as well if you or a friend could put one together.

Anderton
I was serious about the kazoo comment. It's a strong, consistent signal...admittedly not very expressive, but you can tweak that with editing and automation. Probably your best bet would be an electric one, like this model.
 
If you have mobility with your feet and legs, another option is using a set of organ bass pedals, like the StudioLogic MP-113. There are quite a few inexpensive DIY MIDI bass pedal projects as well if you or a friend could put one together.

So I would need a 1/4" to 3.5mm adapter to plug it into my computer? Is a wired kazoo better than a simple (no wire) 1 that would be picked up by my microphone?

What type of mic are you using, the onbard one, a USB one or one through an interface?

Would you be willing to post an audio sample of what you are trying to convert? A simple upload to SoundCloud would suffice if you wouldn't mind sharing it.

I use a Samson USB mic.  I'm not sure I could play a kazoo, breath- and effort-wise. I could try tho.
 
 

honestly, get a MIDI keyboard.  I couldn't play 5 years ago.  Today I can bang out simple 1 line melodies pretty much in time.   I didn't take any lessons.  I just got better from recording music over the years.

Also there is a program called "Cales" and "Chordz" which you can use just the white keys.  It allows you to snap the white keys to the scale you are in:

www.codefn42.com
 
 

Just drag an audio clip onto an empty MIDI track and it converts audio to MIDI.
 
http://blog.cakewalk.com/...dy-convert-it-to-midi/
 
This method seems to work with a mono source OK.  I tried it with a bassline, and got a very close match.  Not much luck with a guitar part, too much going on with chords in the signal.  It did seem to capture the rhythm, but it recorded all notes at the same pitch.  Even so, it could compare with the tapping out a rhythm method, then editing the piano roll or staff view for the pitch.
 
So I would think that a clear voice recording would be a reliable mono audio source for this task.

mettelus
Would you be willing to post an audio sample of what you are trying to convert? A simple upload to SoundCloud would suffice if you wouldn't mind sharing it.

Here are a few phrases from my project. The tempo is supposed to be 105. Did both hum and whistle. Also the last 1 I did legatto and staccato. Not sure how hard legatto/bending is to do with a mod wheel. If anyone tries to convert to MIDI, let me know how long it takes?  Thanks.
 
https://soundcloud.com/hatflyer/phrases

jimlau

mettelus
Would you be willing to post an audio sample of what you are trying to convert? A simple upload to SoundCloud would suffice if you wouldn't mind sharing it.

Here are a few phrases from my project. The tempo is supposed to be 105. Did both hum and whistle. Also the last 1 I did legatto and staccato. Not sure how hard legatto/bending is to do with a mod wheel. If anyone tries to convert to MIDI, let me know how long it takes?  Thanks.
 
https://soundcloud.com/hatflyer/phrases

I took a listen to the phrases, but could not find a download button to access the file.
 
No account required here to post and share a link:
https://clyp.it/
 

sorry..should be downloadable, perhaps under the "more" button.  looks like you need an account for the link you gave?