Is This What You Want? add backing vocals to "Dear Prudence" in late August; he had also joined the backing chorus for "Hey Jude" earlier that month. The songs recorded included "Sour Milk Sea" and "The Eagle Laughs at You", for the A- and B-side of Lomax's debut single on Apple, and "You've Got Me Thinking". Among the guest musicians on the London sessions, much of which would go unused, were Eric Clapton, Ringo Starr, Nicky Hopkins, Klaus Voormann and Paul McCartney. Other participants included drummers Bishop O'Brien and Pete Clark; the former was part of Apple artist James Taylor's backing group, while Clark was
"What Is This Heart?" of 69, based on 32 reviews, which indicates "generally favorable reviews". Ian Cohen of Pitchfork Media gave a very positive review of the album stating, ""What Is This Heart?" makes you initially susceptible and vulnerable, and that’s risky when modern discourse seeks metaphorical blood, allowing people to disclose more than ever without actually revealing anything. So make no mistake, the title of this album is a challenge as well, as How to Dress Well’s modern masterpiece is conducted with the most eternal transparency—Krell asks “what is this heart” and lets you look right into his own." "What Is This Heart?"