Choosing a rare item as a reward occurs in several adventures out today. This creates a question for wizards seeking to gain greater spell power.
We have a 9th level wizard (and 1st level knowledge domain cleric) who will finish an adventure, likely gain a level, and the reward is a choice of a rare (official) magic item.
We recently noticed that the Cli Lyre, a rare Bard instrument, gives five spells: fly (3rd), invisibility (2nd), levitate (2nd), protection from evil and good (1st), stone shape(4th), wall of fire(4th) and wind wall(3rd) each once a day.
Taking one level in wizard would add one sixth level spell slot.
In contrast, for taking just one level in Bard and choosing a Cli Lyre that would give totals 19 spell level "slots" and seven additional spells per day (in addition to the one sixth level spell slot gained as a multiclass wizard.)
This raises the question that if a wizard wishes to gain the greatest number of spell "slots", what is the maximum number of extra spell level "slots" this tier 2 level wizard could gain by choosing a level in a class and a rare magic item?
Note of clarification from a commenter below: We would prefer to restrict the spell level "slots" metric to separate spells or to items with charges. This is to prevent the "infinite" spam of low level spells that things like Boots of Levitation provide which is a different form of power than the intent of this question.