You can use WIDI Recognition System
both for converting mp3 to MIDI or Wave to MIDI and Real-Time recognition.
Real-Time recognition allows recognizing sound directly from microphone,
line input or any other input channel of your sound card or other installed device.
Non Real-Time recognition allows recognizing music recorded as digital audio file
(plain (Wave to MIDI) or compressed wave (MP3 to MIDI, MP1 to MIDI, MP2 to MIDI)
will do as well as audio CD track).
Use WIDI as a music processor which allows some non-MIDI instrument to perform as any other instrument you've got in your MIDI synthesizer
Create a ringtone from any melody you want
Convert CD-tracks directly into MIDI, without using a CD-Grabber
Retrieve music notation from MP3's
Create a preview of your mp3 musical files
WIDI Recognition System includes a real-time audio to MIDI conversion module.
This means that you can use this program as MIDI sound generator for non-MIDI
instruments such as guitar or flute. WIDI can detect notes played by any
instrument in real-time and play it synchronously or store as MIDI command.
Hence one instrument can be replaced with another, for example guitar sound
can be replaced with piano or organ timbre.