Evanescence embarked on the Synthesis Live concert tour across North America, Europe, and Oceania from October 2017 to September 2018, accompanied on stage by a different orchestra in every city.

"[16] Lee acknowledged that the project is a risk, "because you're taking music that already worked, people already liked it and it's been there for a long time, and you're gonna go in and mess with it, change it, and show it to them in a different way that they might not like".

[21] "Imperfection", one of the original songs written for the album, is an electronic-symphonic track that features trip hop beats and a "swaggering cadence" and belting from Lee.

[29] For "The End of the Dream", Lee wanted to re-record it in a way "that exposed the completely post-traumatic healing of a survivor- taking the time to focus on the pain, and then look up and past it, gathering the strength to live on, better [and] stronger.

"[16] On the re-remake of "Your Star", Hunt used a vintage Roland SVC-350 vocoder for some beat processing, which "accidentally began picking up some distorted and very otherworldly sounding Mexican radio station's frequency at the end [of the song]".

[34][35] That day, the album's pre-order and release date of November 10, 2017, was announced,[34][36] and the band uploaded YouTube video clips titled Inside Synthesis of their process in the studio.

[43] Renowned for Sound's Rachael Scarsbrook regarded it as Evanescence's "most ambitious project to date", writing, "there is a beating heart and spirit within this release that still hurts and evokes the most cathartic of responses".

[51] Suzy Exposito of Rolling Stone said that the remake of "Bring Me to Life" is an "act of artistic justice" for Lee and highlighted the album's two new "ambitious" songs.

"[46] Chad Bowar of Loudwire considered the album "dynamic and compelling", and praised Lee's vocals, the mix of various instruments and the production, describing it as "grandiose and bombastic in parts, quiet and subdued in others".

[53] Siena Yates of The New Zealand Herald complimented Lee's voice and the "cinematic" classical foundation of Synthesis but found the album "weird" and "largely unnecessary", believing that stripping down and reworking the hits removed the "nostalgia" and "hooks" that made Evanescence stand out in their early days.

[50] Writing for Classic Rock, Stephen Dalton said that the "guitar-free remakes have a windswept grandeur and widescreen sonic palette lacking in the original recordings", and complimented the new songs, dubbing the album a "successful experiment".

[47] Blabbermouth.net deemed it Evanescence's "most ambitious effort to date", writing that "Lee's incredible vocal range and the group's expressive, multi-layered music naturally lends itself to orchestral accompaniment", creating a "truly dynamic, cinematic sound" while the passion "undoubtedly shines through".

[45] Variety's Roy Trakin wrote that "Lee firmly re-establishes herself as one of rock's pre-eminent vocalists", while the songs become "full-throttle, wide-screen epics" and the album evolves Evanescence's sound.

[56] Catherine Morris of Metal Hammer considered Synthesis "an ambitious and unexpected move", stating that it impels Evanescence's music "into a new, alternate dimension", giving songs an "ethereal, cinematic makeover" and drawing the listener's attention to the "core melodies".

[49] Jim Fusilli of The Wall Street Journal felt that "the shift in style isn't without its risks" and "for the most part, the new approach works well" while the electronic percussion "gives the music yet another new trait".

[57] Reviewing for Kerrang!, Paul Travers expressed that the orchestral elements aren't a radical transformation as Evanescence's rock music "works with space and texture and [is] built around Lee's vocal and piano".

[48] AllMusic's Stephen Thomas Erlewine called Synthesis a "successful fusion" that "amounts to a step forward" for Evanescence, regarding it a "natural fit" for Lee, whose "powerhouse vocals often wrestle the orchestra into submission", and the "layered, skittering electronic rhythms" help give it "a steel spine".

[40] Writing for Gig Wise, Catherine Verrechia said that introducing an orchestra feels like a "natural progression", and "surprisingly, the music still has many doses of heavy, atmospheric aspects".