I googled "ultima online discord training" and found this:
http://www.uopowergamers.com/s-discord_aos.shtml
Get your music back down to 100 and you'll gain the other bard skills faster.
That guide is a bit dated.. And having music over 100 doesn't make you gain slower specifically, it just makes creatures easier to bard overall and that makes it more difficult to find creatures to gain from at GM skill and above.
As for a guide, in general you want to bard creatures that you have between 30 and 70 percent chance of successfully barding. The easiest way to determine the success rate is to use a
barding calculator.
Starting with 110 music and 30 discord, and assuming you have a character with positive karma, here's a safe way to gain (Make sure you use normal and not exceptional instruments):
30-45 Shadow wisps at one of the Ilsh champ spawns.
45-70 Get yourself friended to the solen ants, and you should be able to discord them safely. Workers up to 55, then warriors and queens to 70.
70-80 Back to the Ilsh champ spawns for pixies
80-90 Wandering healers at Healers grove in Ilsh
90-105 Ethereal warriors
105+ Cu sidhes
After you hit 90 discord gains slow way down. After about 105, gains from normal gameplay are almost nonexistent besides the guaranteed gains.