If you are looking for a way to convert MIDI audio (.midi) to text format (.txt), the easiest way would be to use some of the online converters that offer exactly this type of conversion. Probably used to transcript the notations or something.
Convert MIDI-sequention sound to Simple text.
We have found one software suitable in our database for this conversion.
On-line services software - convert midi to txt on web
An online converter for MIDI format
Convert from midi file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.