Musical style thumb|alt=Poster advertising a concert programme at Musikforeningen with items by Beethoven, Bach, and lastly Nielsen's fifth Symphony, 1922|Poster for premiere of Carl Nielsen's Fifth Symphony, 1922In his Lives of the Great Composers, the music critic Harold C. Schonberg emphasizes the breadth of Nielsen's compositions, his energetic rhythms, generous orchestration and his individuality. In comparing him with Jean Sibelius, he considers he had "just as much sweep, even more power, and a more universal message". The Oxford University music professor Daniel M. Grimley qualifies Nielsen as "one of the most playful, life-affirming, and awkward voices in twentieth-century music" thanks to the "melodic richness and harmonic vitality" of his work. Anne-Marie Reynolds, author of Carl Nielsen's Voice: His Songs in Context, cites Robert Simpson's view that "all of his music is vocal in origin", maintaining that song-writing strongly influenced Nielsen's development as a composer.
musICAL sTYLe Thumb|aLT=pOster aDvertising A conCerT prograMme at musikforeNIngen WITH Items bY BEEtHOveN, Bach, anD laStly nieLsEN's fiFtH syMpHONY, 1922|poster For PremIere of Carl NieLsen'S fIftH sYmpHony, 1922In his LiVES Of the GrEAt comPosers, tHE MuSic crITIC HaRold c. scHonBerg emphasiZes thE breaDtH Of NiElSen'S CoMpoSitIonS, His: eNERgeTIC rhYthms, gEnErous orchestRaTion And his indiVidUAlity. in CompaRing hIm WITh jeAN sibELIuS, He ConsidERs HE Had "jusT as MucH sweeP, EvEn moRE PoWer, aNd a More UnIveRSaL MesSaGE". thE oxford UNIVeRsity MuSic ProfeSsoR DANiel m. grimley qUalIfIes NiElsen As "oNE Of The Most Playful, lIfE-affiRMIng, aND awkWArd voICeS iN TWentIEtH-CenTUrY mUsic" ThaNks to The "mElodic riChneSS AnD haRmOnic vITalItY" of his Work. aNnE-mAriE reyNolds, author of CaRl NIelSEn's voice hIS SONgs iN CoNTExT, citEs robeRt siMpSoN'S VIew thaT "all of hIS MuSIc is voCal in orIGIn", MaInTaininG thAT song-wrItinG strongly infLueNCEd nIElsen's dEvELoPment AS a coMPOSEr.