To make a QCP file louder, you need to increase the volume of the WAV file before you convert it.
To make a MP3 file louder, you need to decode the MP3 to a WAV file and increase the volume of the WAV file. Then convert it back to MP3.
To make a MIDI file louder, you will need a program such as Anvil Studio to edit the MIDI and make the individual tracks louder.
Someone even reported that Adobe Audition has built-in filters to decrease bass and increase vocals and make the song louder overall. It is said to work great.