In my opinion, it would most probably be the piano.
If you're going to ask why, it's simply because of the sound projected by the piano.
It's one of the most soothing and it has a calming effect on the listener.
Another instrument could be a harp.
The harp sounds somewhat like the piano, with it's soothing sound.
So since it's poetry you're asking about, I'd really recommend either a piano or a harp.
Piano
Piano, although other instruments could accompany it.
Mridangam is a percussion instrument. It is generally used to accompany south Indian classical music (Carnatic Music).
Many instruments go well with a guitar. The drum and piano are two good instruments to accompany a guitar.
Erato - muse of love poetry The cithara or kithara, it was an ancient Greek musical instrument in the lyre family Nowadays the word kithara has the meaning of guitar kithara----> guitar
The lyre, created and given to him by Hermes.
The type of poetry which deals mainly with the private thoughts and emotions of an individual is called Lyric poetry. Lyric comes from lyre - the lyre being an instrument that singers used to accompany themselves with before the guitar developed to fulfil the same function. If it would make a reasonable song-lyric, it is probably a lyric poem.
The accordion
Piano
The Ipu, Hawaiian gourd percussion instrument used to accompany Hula Dancers
harp
AulosThe aulos.
AulosThe aulos.
The aulos.
The aulos. This instrument is a two-chambered pipe which was historically used to accompany performances of tragic plays.
The chordophone used in ancient Greece was the kithara. It was a lyre-like instrument with a large wooden body and several strings that were plucked to create music. The kithara was popular in both formal settings, such as performances of lyrical poetry, and as an accompaniment for traveling musicians.
castanets