Dependency on SoundFont Libraries
MIDI files don’t contain any sounds, just codes or control messages that refer to the computer’s sound samples. MIDI standard defines the message codes for musical events that include the start of a note, its pitch, length, volume, and musical attributes, such as vibrato. It also defines codes for various button, dial, and pedal adjustments.
The audio tool, or sound card, uses its capabilities to create music according to those messages. This process is called "sound synthesis", and the device which produces the sound is called as "synthesizer". So, if a computer has poor-quality MIDI library or dissimilar instruments’ sound, MIDI composition plays back in a different way, and, probably, with worse quality.
Lack of support by various devices
Most of the media players, including all smartphones and tablets, support MP3 format, unlike MIDI format.
Lack of support by various audio tools
Unlike MIDI, MP3 and WAV files can be imported in nearly all audio editors and sound improving tools. So, after conversion, you'll be able to polish and edit your compositions through any MP3 or WAV supporting audio software.
Therefore, the best way to listen and improve your MIDI compositions is to convert them to MP3 or WAV formats first. Our applications, including MIDI to MP3, help to convert MIDI message files into a real music, which will sound same on all devices and systems.