For the purpose of analysis the music scholar Jane Glover has divided Monteverdi's list of instruments into three main groups: strings, brass and continuo, with a few further items not easily classifiable.
The strings grouping is formed from ten members of the violin family (viole da brazzo), two double basses (contrabassi de viola), and two kit violins (violini piccoli alla francese).
The viole da brazzo are in two five-part ensembles, each comprising two violins, two violas and a cello.
The brass group contains four or five trombones (sackbuts), three trumpets and two cornetts.
The continuo forces include two harpsichords (duoi gravicembani), a double harp (arpa doppia), two or three chitarroni, two pipe organs (organi di legno), three bass viola da gamba, and a regal or small reed organ.
Outside of these groupings are two recorders (flautini alla vigesima secunda), and possibly one or more citterns—unlisted by Monteverdi, but included in instructions relating to the end of act 4.

Instrumentally, the two worlds represented within the opera are distinctively portrayed.
The pastoral world of the fields of Thrace is represented by the strings, harpsichords, harp, organs, recorders and chitarroni.
The remaining instruments, mainly brass, are associated with the Underworld, though there is not an absolute distinction; strings appear on several occasions in the Hades scenes.
Within this general ordering, specific instruments or combinations are used to accompany some of the main characters—Orpheus by harp and organ, shepherds by harpsichord and chitarrone, the Underworld gods by trombones and regal.
All of these musical distinctions and characterisations were in accordance with the longstanding traditions of the Renaissance orchestra, of which the large L'Orfeo ensemble is typical.

Monteverdi instructs his players generally to "[play] the work as simply and correctly as possible, and not with many florid passages or runs".
Those playing ornamentation instruments such as strings and flutes are advised to "play nobly, with much invention and variety", but are warned against overdoing it, whereby "nothing is heard but chaos and confusion, offensive to the listener".
Since at no time are all the instruments played together, the number of players needed is less than the number of instruments.
Harnoncourt indicates that in Monteverdi's day the numbers of players and singers together, and the small rooms in which performances were held, often meant that the audience barely numbered more than the performers.

Of all the instruments used in the original performance of L'Orfeo three instruments are no longer used in modern society: The double harp, The cornetto, and the regal.
The Cornetto was a woodwind that was comparable to a trumpet.
The Double harp was a string instrument that is similar to a modern-day harp.
The regal was a keyboard similar to a modern-day harmonium, and sounds like the reed pipes of pipe organs .These instruments were used almost as characters in the play.
Particularly the regal was used in many scenes depicting Hades to symbolize death and mirroring the music of a modern-day funeral procession.
For the purpose of analysis the music scholar Jane Glover has divided Monteverdi's list of instruments into three main groups: strings, brass and continuo, with a few further items not easily classifiable. The strings grouping is formed from ten members of the violin family (viole da brazzo), two double basses (contrabassi de viola), and two kit violins (violini piccoli alla francese). The viole da brazzo are in two five-part ensembles, each comprising two violins, two violas and a cello. The brass group contains four or five trombones (sackbuts), three trumpets and two cornetts. The continuo forces include two harpsichords (duoi gravicembani), a double harp (arpa doppia), two or three chitarroni, two pipe organs (organi di legno), three bass viola da gamba, and a regal or small reed organ. Outside of these groupings are two recorders (flautini alla vigesima secunda), and possibly one or more citterns—unlisted by Monteverdi, but included in instructions relating to the end of act 4.
Instrumentally, the two worlds represented within the opera are distinctively portrayed. The pastoral world of the fields of Thrace is represented by the strings, harpsichords, harp, organs, recorders and chitarroni. The remaining instruments, mainly brass, are associated with the Underworld, though there is not an absolute distinction; strings appear on several occasions in the Hades scenes. Within this general ordering, specific instruments or combinations are used to accompany some of the main characters—Orpheus by harp and organ, shepherds by harpsichord and chitarrone, the Underworld gods by trombones and regal. All of these musical distinctions and characterisations were in accordance with the longstanding traditions of the Renaissance orchestra, of which the large L'Orfeo ensemble is typical.
Monteverdi instructs his players generally to "[play] the work as simply and correctly as possible, and not with many florid passages or runs". Those playing ornamentation instruments such as strings and flutes are advised to "play nobly, with much invention and variety", but are warned against overdoing it, whereby "nothing is heard but chaos and confusion, offensive to the listener". Since at no time are all the instruments played together, the number of players needed is less than the number of instruments. Harnoncourt indicates that in Monteverdi's day the numbers of players and singers together, and the small rooms in which performances were held, often meant that the audience barely numbered more than the performers.
Of all the instruments used in the original performance of L'Orfeo three instruments are no longer used in modern society: The double harp, The cornetto, and the regal. The Cornetto was a woodwind that was comparable to a trumpet. The Double harp was a string instrument that is similar to a modern-day harp. The regal was a keyboard similar to a modern-day harmonium, and sounds like the reed pipes of pipe organs .These instruments were used almost as characters in the play. Particularly the regal was used in many scenes depicting Hades to symbolize death and mirroring the music of a modern-day funeral procession.
L'Orfeo