Your Charisma score increases by 3, but your Strength score is reduced by 1.

Song dragons live vast amounts of time, but in their human forms they never appear to be less than 18 years of age, and they seemingly halt aging around an apparent age of 35.

Song dragons can be of Chaotic alignment. They are almost exclusively Chaotic Good or Chaotic Neutral, but given the right circumstances they could lean on the side of Chaotic Evil.

You speak Common, Draconic, and one language of your choice.

Song dragons count as Medium-sized creatures when in human form, and share similar height and weight with humans. When in their natural draconic form, their size is Large.

Your base walking speed is 30 feet.

You gain proficiency with two tools or musical instruments of your choice. In addition to this, you have advantage on all performance checks.

[Warning from your friendly neighborhood Crossark: This is going to get preeeeeetty complicated. I'm taking an objectively overpowered creature and trying to make it into a playable character race because I thought the whole gimmick of the Song Dragon creature type sounded like it would be fun to play with and held a lot of potential for roleplay synergy -- if it could be implemented properly. My core idea going into this particular trait was that it should have a lot of versatility, but be enough of a hassle to use that it would be only be viable in near-emergency situations, thereby encouraging the player to either be in their human form for the majority of the game or make heck of a lot of sacrifices. Song dragons are canonically averse to using their draconic abilities, after all, and while I like to design the "racial outsider" character as much as the next guy, I don't want a first-level player character who happens to rebel against the typical characteristics of their race to get access to god mode as a result. So, I had to get really specific with this stuff -- I hope you'll bear with me.]

Starting at level 5, you may take on your draconic form once per day when in a tight situation. You may take an action to transform into a Dragon of Large size when you are bloodied (half of less of your total health); you may also spend your reaction for a certain round of combat to transform if you've just taken bloodying damage from an attack. However, you are not restricted to using this ability purely in combat, so long as you are bloodied. When you transform, any items you had on your person don't transform with you -- they fall to the ground beneath your dragon form. You must transform back to your human form if you exit combat, you have spent 3 hours in your dragon form, or you wish to take a short or long rest.

 While in this form, you have a base walking speed of 40 feet, a base climbing speed of 40 feet, and a base flying speed of 80 feet. When flying, you have Average maneuverability. The hit points of your draconic form are calculated by subtracting half of however many points of damage you took prior to transforming from 119 (i.e.: Total = 119 - 1/2[damage taken]). Your tough, scaled hide provides you natural armor; your AC is 17.

If your Strength score is less than 18, it increases to 18. You also have advantage on Intimidation checks made in this form.

You cannot cast spells when you are a Dragon. You have the following four attacks:

• Bite attack: This attack has a range of 10 feet. On a hit, your bite deals 2d8+4 piercing damage to a target. When you use this attack to attack a target more than 5 feet from you, you make an easy target out of your extended neck; creatures gain advantage on attacks against you until the start of your next turn.
• Claw attack: This attack has a range of 5 feet. On a hit, you deal 2d6+4 slashing damage to a target. You may use this attack twice in succession; if you have a feat or other trait that would give you an additional attack, you may not use that attack between two claw attacks, as doing so cancels your second claw attack. You may use your claw attack to target two different creatures in range.
• Tail swipe attack: This attack has a range of 5 feet. On a hit, your tail deals 1d12 bludgeoning damage to a target.
• Breath attack (usable once per transformation): You breathe out a 30-foot cone of ionized gas. Each creature in range must make a DC 14 saving throw. Creatures take 6d8 lightning damage on failed save or half of that on a successful one. Affected creatures who fail their saves are also poisoned until the beginning of your next turn.

[Special thanks to Reddit users stitchlipped and Kylasaurus_Rex, whose work on their homebrewed Monster Manual entries for the Song Dragon creature type provided a valuable jumping-off point for some of the finer details of this character race adaptation.]