[5] Muscato took part in the ITV show Stars in Their Eyes Kids at age 15, auditioning for the contest, thanks to a tape submitted by his mother.

[6] On 29 October 2006, at the London Wicked day celebration, he participated in the singing contest held during the event as one of ten, with the song Dancing Through Life.

[9] Muscato later made his West End debut following the show's transfer to the Novello Theatre,[10] where it played from March 21, 2009, until its early closure on May 30, 2009.

The tour made stops in Manchester, Norwich, Birmingham, Edinburgh, and Paris, until it settled in the Barbican Theatre from September 14, 2010, to October 2, 2010.

Following the tour of Les Misérables, Muscato joined the musical, Love Story, as an ensemble cast member, as well as understudy for Oliver Barrett IV.

Later during the 85th Academy Awards, Muscato was offered the opportunity to be flown to Los Angeles to perform alongside the main cast of the film.

Following its 2012 run Off-Broadway, Dogfight was announced in May 2014 to be receiving both its European and UK premiere in the Southwark Playhouse, for a month-long engagement from August 13, 2014, through September 13, 2014.

[18] This marked his first lead role in a professional production, playing opposite Laura Jane Matthewson, who was cast as Rose Fenny.

[24][25][26] In October 2015, Muscato joined the Welsh National Opera production of Sweeney Todd, touring around the United Kingdom.

[29] As part of the VAULT festival, Muscato starred as the titular character in the one-man musical Stay Awake, Jake for four days, from February 3 to 7, 2016.

[30] In April 2016, Muscato starred in a workshop alongside Melissa Errico for The Gold Room, a musical from the creative team of Michael Feinstein and Warner Brown.

[31] The London production of Lazarus was announced on July 25, 2016, following the death of the musical's author David Bowie earlier in the year, to be playing at the King's Cross Theatre from November 8, 2016, through January 22, 2017.

[33] The London production featuring Muscato was filmed and eventually screened for one night at the Kings Theatre on May 2, 2018, played alongside a live accompaniment by the original band.

In April 2018, Carrie Hope Fletcher was announced to be playing the role of Veronica Sawyer in the European premiere and full staging of Heathers in The Other Palace.

As announced, the show returned after its break for its transfer to the West End in the Theatre Royal Haymarket, which received updates to its script, as well as a new song.

In a review for the show, britishtheatre.com writer Danny Coleman-Cooke called Muscato "the stand-out performer" and praised his acting and comedic timing.

[41] Writing for The Independent, Paul Taylor praised Muscato's vocal ability and performance that "[combined] seductive, witty charm and a haunted, high-risk insecurity".

[53] On August 15, 2019, Muscato was announced to be playing the lead role of Tony in West Side Story, alongside Adriana Ivelisse as Maria.

[54] To promote the show, the channel released 40-second clips of Muscato singing "Something's Coming" on September 25, 2019, and "Tonight" alongside Ivelisse on October 14, 2019.

Muscato appears in 2019 BBC TV historical drama series The Trial of Christine Keeler as a police officer in the first episode.

[16] With his former castmate Laura Jane Matthewson, Muscato performed as a part of Back Garden Busk in Chorleywood in August and September 2020, socially distanced from the audience.

[59] In December 2020, Muscato worked with The Umbrella Rooms, performing several songs as a part of a live prerecorded concert on the website.

[60] At the end of 2020, The Colour of Spring directed by Paul Andrew Kimball premiered on several film festivals, starring Muscato as leading man Sam Cameron, opposite Alexa Morden as Sarah.

[63] After the original extension of the Les Misérables staged concert was suspended on December 16, 2020, after only 10 performances due to local COVID restrictions, the show was announced to be returning on March 10, 2021.

[65] On December 3, 2021, Toy Soldier Productions announced that it was developing a musical based on Shakespeare's play Macbeth, and that Muscato was part of the cast.

[68] Continuing with his venture into on-screen television acting, Muscato appeared on British medical drama Doctors as Wes Corbett, a guitarist squabbling with his bandmate.

[83] On September 21, 2022, Muscato was announced to be starring in a one-night-only concert production of Once alongside Carrie Hope Fletcher, which would take place on March 12, 2023, in the London Palladium.

[88] Later in October, Muscato played Matt "Matty" Flamhaff in a workshop run of the musical 13 Going on 30 at Battersea Arts Centre.

[90][91] On October 17, 2024, Donmar Warehouse[92] announced on Instagram that Muscato would be starring in the London premiere and Off-West End production of Natasha, Pierre & The Great Comet of 1812 as Anatole Kuragin from December 2024 to February 2025.

[93] On February 6, 2025, it was announced Muscato would star in the titular role for the London and West End premiere of The Great Gatsby opposite Frances Mayli McCann as Daisy.