Tyagaraja seems to have received a hint of his end on this earth a few days earlier. He describes this realization in this kruti.

Sahana raagam
giripai nelakonna raamuni guri tappaka kamTini
parivaarulu viri suraTulacae nilabaDi visarucu kosarucu saevimpaga .. giripai
pulakaamkituDai aanamdaaSruvulu kanulanimDaga
kaluvarimca gani padi pooTalapai kaacedanane tyaagaraajaaptuDu .. giripai

Summary:
Rama who took abode on the hill, unerringly I saw
As the attendants stood around with flowered fans, diligently worshipping Him, .. on the hill
Immersed in thrill, tears of delight overflowing the eyes, as I called out thus,
the One dear to Tyagaraja, noticing me, promised to save me in ten half-days, .. on the hill

Notes: Tyagaraja received a vision of Rama, sitting in glory on the hill, attended by his full retinue. As Tyagarja stood speechless, moved to tears by the overpowering bliss of devotion, Rama promised that He will save yagaraja in 5 days ("pooTa" is Telugu word for half-day or part of a day). Appropriately, this kruti is set in Sahana raagam which is well-known for its ability to project karuNa rasa. One has to listen to the late M.D. Ramanathan sing this kruti to get a feel for what Tyagaraja must have experienced in that vision. This rendition is available on an old HMV album.

It appears that Tyagaraja received "sanyasa" (renunciation) vows at this point and spent the remaining 5 or so days as a hermit. That's why he is called "Tyagaraja swami" (Saint Tyagaraja) today. He is also respectfully called "sadguru" (true teacher), an epithet perhaps started by his numerous disciples. He gave up his physical body (attaining 'samadhi') on pushya bahuLa pancami (5th day in fortnight of waning moon in the month of pushya, 6 Jan 1847 in Gregarian calendar). This day is commemorated every year in Tiruvayyaru as Tyagaraja Aradhana Utsavam (of course, the Aradhana Utsavams in the rest of the world take place at times more convenient to organizers and participants). The day starts with prayers at his samadhi and pooja and abhisheka to his deity. This is followed by "Uncha vrutti" where a male musician is dressed up like Tyagaraja and a troupe of musicians goes around a few streets singing his songs, receiving alms, as Tyagaraja and his disciples used to do. The main event starts with group rendering of Tyagaraja's ghana raaga panca ratna krutis (five gems in ghana ragas) at the festival venue by all the assembled musicians. Hundreds of musicians pay tribute to the saint over the next three days, rendering his compositions.

To conclude with the traditional and mandatory benediction,
souraashTra raagam
pavamaana sutuDu baTTu paada + aravindamulaku .. nee naama roopamulaku nitya jaya mamgaLam
prahlaada naaradaadi bhaktulu pogaDucumDu .. nee naama
raajeeva nayana, tyaagaraaja vinutamaina .. nee naama

Summary:
To your lotus feet pressed fondly by Hanuman, son of Wind God, and to your name and form, victorious mangalam always Praised by devotees such as prahlada and narada .. your name and .. Oh lotus-eyed One, exalted in Tyagaraja's singing .. your name and ..

Notes: This kruti is the last benediction in Tyagaraja's musical drama "prahlaada bhakti vijayam". Over the years, it had become the de facto mangalam for Carnatic concerts.