To help me practice music, I'd like to make a sound (hum, sing or whistle into my microphone) and have the corresponding note displayed on screen. A program that gives feedback live (while I play) would be ideal, but giving feedback on a recording would also be acceptable.
I've been looking for a program like this for quite some time. I would love a program that you can hum and it will translate it into musical notation. But for the time I user a tuner program on my cellphone. There are several for linux listed in freshmeat so check them out, for something that works for you.
http://freshmeat.net/search?page=1&q=tuner&submit=Search&with=66&without=
For music practice CANTA-game.org is reputed to run in Linux and will pick up acoustic instrument via microphone and compare in real time to your previously input song note for note and give an instant colour-coded comparative result on screen.
Use tonescope.net. Hate to reply to a necro thread, but just in case someone stumbles upon this and wants the answer, I made a website recently for just that. It uses the sound from your microphone to return note name, octave and pitch in real time. Hope you find it useful!