Introduction to MIDI and Computer Music: Making AAC and MP3 Files with iTunes
AAC and MP3 are both lossy audio compression formats. AAC is the default format used by iTunes. It produces better audio quality than MP3 for a given data rate (e.g., 128 kbps) and is playable in almost all software that can play MP3 files.
CAUTION: If your music contains sounds copyrighted by other people, and you don’t have permission to use those sounds, then think twice about uploading your music to a web site. That counts as distribution, and the copyright holder may hold you accountable for your use of their sound.
Before making an AAC or MP3 file, you first must export your mix as an uncompressed audio file, either WAVE or AIFF.
To find the End marker, look at the right side of the sequence horizontal scroll bar for the vertical symbol circled in red below.
Scroll this part of the sequence into view until you can see the End marker in the time ruler: the small box enclosing E.
Drag this marker to the point where you no longer hear any sound sustaining from your last notes, such as delay or reverb tails. Please leave 2-3 seconds of silence before the End marker.
Here’s how to make an AAC file using the iTunes program available on the M373 Macs. (These instructions are correct as of iTunes 220.127.116.11.)
Because of the way iTunes is set up in our room, this often will present you with an annoying series of choices. Just agree to the license, and say “No Thanks” to the offer to share your library details with Apple.
Soon a new file will appear, with the same name as your mix file. So how do you know which is which? Right-click on the column headings strip, which gives the name, time, artist, etc. Choose Bit Rate from the list of column names. Your mix file will have a 1,411 kbps bit rate, while the AAC file will be 256 kbps.
If for some reason dragging the file doesn’t work, right-click on it in iTunes, and choose Show in Finder. This will show you a Finder window for the folder that contains both your files (e.g., the WAVE and the AAC).
If you want to make an MP3 file instead of an AAC file, insert these steps between steps 3 and 4 above. Bear in mind that AAC is higher quality than MP3, for equivalent data rates, and is widely supported in software now.
When you choose the Convert command, mentioned above, it will be called Create MP3 Version.