Free Audio Converters to go from m4a to mp3 abound, take your pick:

http://www.bing.com/search?q=free+audio+...p;sp=-1&sk=

If the song you have doesn't line up all the way through after setting bar 1 it is because the song may not stay locked at one tempo throughout.

After you Set Bar 1 position, take a look to that button's immediate right.

"Tap Barline F8"

Hit Play and tap the F8 key on the first beat of every bar as the song plays. Don't worry if you miss, you can hit Stop and hit Play and start over again. Helps to count to yourself as you do this. Once that has been established for the whole song, then when you tell ACW to include the Tempo Map, it will have the Tempo data to work with. There will be a red outline around each bar number in BiaB where it had to invoke a slight tempo change to track with your audio clip.


--Mac