It's here: Random Advancement Bard

Minstrelsy is a contagion that strikes as many as 1 in 12 adventurers.  To play a Random Advancement Bard, you must begin as a member of any of the more respectable classes, such as Toad Licker, Sewer Urchin, or Pustule Piercer.  Just grab a ukulele and begin hey-nonny-nonnying your way across the countryside.

The Bard

A member of any class who possesses a Charisma of at least 12, a stringed instrument (30gp new) and a lowered sense of self-worth may elect to become a Bard at any time.  You continue to follow all the normal rules for well-adjusted members of your original class, but each time your character advances a level you substitute one or two rolls (your choice) on your normal advancement chart for rolls on the one below.

Note 1:  You cannot use any of the song-based powers below unless both your voice and your instrument are in working order.

Note 2: Nothing on the chart below functions when wearing any armor heavier than chainmail. Even stuff that should. On the other hand, stuff below that shouldn't work in chainmail totally does.

01-03  You get nothing.  No one said show business was easy.

04-09  You get generally better at fighting: +1 to-hit

10-25  You get +1 saves

26-27  +d4 hit points

28-35  If you are already a spell caster, gain a spell slot as normal.  If not, pick your new side gig of Wizard, Druid, or Illusionist and gain the abilities of a first level caster.  Every time you roll here after that, advance by one level in spellcasting ability.  New amateur wizards and illusionists should generate a starting spellbook using the normal rules.  How you happened across such a thing is up to you and the DM to decide, but you probably stole it.

36-43  If you are already a thief or otherwise get Thief Abilities (like monks and assassins do), then advance one level in your thiefly skills.  Otherwise, gain the skills of a 1st level thief and advance one level every time you roll this result again.

44-50  Work the crowd: By playing and singing for an hour or two you can gain d4gp worth of coins in a village, d6gp in a town, or d8gp in a city.  You must roll a Cha check to get the loot but if you get a 20 the crowd goes all angry mob on you.  Every time you roll this result you can increase the dice sizes, until it maxes out at d10/d12/d20.  Reroll this result after that.

51  Gain +1 Dex.  If you already have max Dex, gain +1 saves vs. anything that could possibly be dodged.

52-53  Cunning Linguist: gain knowledge of a language of your choice

54-55  Item Identification.  Once per session you can identify any magic item with an Int check.  Subsequent rolls grant additional attempts per session.

56-57 Countersong:  Once per session you can negate sonic effects and attacks with your own music.  You can do this for a number of rounds equal to your level plus your Con bonus (minimum 1).  Reroll if you get this result again.

58-59 Fencing prowess:  Gain proficiency with swords, scimitars, and shortswords if you did not already possess it.  Otherwise you are +1 AC when wielding such a sword and not surprised, flat-footed, or otherwise subject to sneak attack.  Gain +1 more AC for each reroll of this result.

60 Dancing fool: When affected by Otto’s Irresistible Dance, the poison of the tarentella spider, the music of korreds, etc., you will dance upon a missed save just like everyone else but you may act normally while doing so.

61-62  Sorcerous secret:  Gain a random standard first level MU spell as a daily power.  Unless you already cast MU spells, in which case roll from a list in some more obscure book of MU spells.  If you get this result again gain a 2nd level spell, then a third, etc.

63-64 “Was it over when the Germans bombed Pearl Harbor?”  Once per session you may give a rousing but nonsensical speech prior to the start of a combat.  All allies who can hear your oration gains +1 to-hit for the ensuing battle and NPCs gain +1 morale.  Reroll this result if it occurs again.

65-66  Impress the ladies/lads.  Once per session you can play a love song and make a Cha check to seduce a member of any sentient species, provided their orientation includes your gender.

67-68  Hard drinker.  Once per session you may down a skin/bottle of ale or wine in one turn to replenish d6 hit points.  If this is already a rule in your game, then increase to d12 hit points.  Each time this is rerolled you may down an additional skin/bottle, but the DM is allowed to invoke inebriation rules after the first such occurrence.

69-70  Druid secret: Gain a random standard first level Druid spell as a daily power.  Unless you already cast Druid spells, in which case roll from a list in some more obscure book of Druid spells.  If you get this result again gain a 2nd level spell, then a third, etc.

71  Pied piper: Once per session you can use your music to charm any group of identical monsters of less than one hit die, up to a number equal to your level plus Charisma bonus.  The monsters stay charmed for no more than three session or until you charm monsters of another species.

A bard if I ever saw one.

72-73   Illusionist Trickery: Gain a random standard first level Illusionist spell as a daily power.  Unless you already cast Illusionist spells, in which case roll from a list in some more obscure book of Illusionist spells.  If you get this result again gain a 2nd level spell, then a third, etc.

74-75  Gain +1 Charisma.  If you already have max Cha then gain a 1st level henchperson of a random class.

76-77  Magic instrument prowess.  When using a magic instrument not specifically for Bards it is generally 50% more effective in your hands.  Reroll if you get this result again.

78  The skin of your teeth.  The next time you die you mysteriously reappear somewhere safe d6 days later, bereft of all equipment and treasure save for one item of your choice.  Note that your undergarments count as an item.  You may do this exactly once.

79-80 Music soothes the savage beasts.  Before combat is joined you can spend a round to play a little ditty to placate any creature of animal or less intelligence.  If it fails a save versus spells it will not attack and insteads sits idly for d6 turns or withdraws (50/50 chances).  This effect is negated by attacking the monster, stealing its treasure, yelling at it, etc.  You may do this once per session.  Reroll if you get this result again.

81 Repairer of Reputations: Pick a person that you have been talking up in your original compositions.  They’re a little famous now.  Everyone in the local region is now +1 reactions with that person.  Yes, you can use this for yourself.

82-83 Place lore:  Once per session you can know something useful about a place relevant to the current adventure.  Reroll if you get this result again.

84-85 Dual wield:  You can make an extra melee attack with no penalty by wielding a dagger in your left hand.  (You gain dagger proficiency if you don’t already have it.)  However, you are a bit of a danger to your friends.  If you roll a natural 1 with the dagger attack you automatically stab the nearest friendly.  If no ally is within stabbing range, then you must throw the dagger at the nearest adventure buddy.  If they are out of range they’re safe, otherwise roll to-hit.  Reroll if you get this result again.

86-87 Noble lore: You know all the ins and outs of heraldry, family trees, royal gossip, etc.  Once per session and upon request the DM must supply you with a juicy tidbit that can help you in your present situation.  Reroll if you get this result again.

88  You may declare any magic item you find to be an Ancient Bardish Artifact.  This has no effects on the item or your ability to use it, but everyone else in the party must honor your claim to it unless they are willing to resort to violence.  You may do this exactly once.

89  You gain a random mutation.  Because fuck you that’s why.

90 El Kabong!  Once per session you may use your precious lute or whatever as a bludgeon.  This is so surprising that you get +2 to-hit, doing d6 damage and the foe must save versus paralyzation or be knocked out cold.  However, if you successfully hit then your instrument is shattered.

91-92 Riddle or fiddle:  The next time you are confronted by a monster but a fight hasn’t started yet, you can challenge them to either a song or riddle contest.  Negotiate the stakes and both sides roll d20, higher roll winning.  You have no mechanical advantage to the roll but the monster will automatically accept the challenge and abide by its results.  You may do this exactly once.

93  Ruiner of Reputations:  Pick someone you dislike.  Your latest original compositions have all contained digs at them.  They are now -1 reactions for everyone in the region, but there is a 1 in 6 chance they find out it is your fault.

94  Silver-tongued devil.  Once per session you may tell of lie of nearly any magnitude and a number of creatures equal to your level will believe it.  Reroll if you get this result again.

95  Use any item.  You can use any magic item for any class with a successful Int roll per usage. If you roll a 20 you experience some sort of mishap determined by the DM.

96  Lucky bastard: Once per session you can reroll any roll after you know the result.  The second roll applies whether it is a better result or not.

97  Admirer.  Gain a creepily devoted 0-level loser as a henchweenie.

98-99  Gambler: When resolving gambling attempts you always get the better of two rolls or the draw of an extra card or whatever.  You can take the best of a third draw/roll/whatever but there’s a 1 in 6 chance your cheating is detected.
100  Song of Making:  Bards know that the world was called into existence by means of a Great Song.  You know just enough of this primordial music to call into existence any nonliving object on your ruleset’s price lists, including things like a ship or a tower.  You can do this exactly once.